Expanded toc-like environment

Here's a possibility using the titletoc package to generate the partial ToCs and a variation of Martin Sharrer's answer to Table of Contents with additional description of entries to include the additional section description in the partial ToC:

\documentclass{book}
\usepackage{titletoc}
\usepackage{environ}
\usepackage[inline]{enumitem}
\usepackage{lipsum}

\makeatletter
\def\@nodottedtocline#1#2#3#4#5{%
  \ifnum #1>\c@tocdepth \else
    \vskip \z@ \@plus.2\p@
    {\leftskip #2\relax \rightskip \@tocrmarg \parfillskip -\rightskip
     \parindent #2\relax\@afterindenttrue
     \interlinepenalty\@M
     \leavevmode
     \@tempdima #3\relax
     \advance\leftskip \@tempdima \null\nobreak\hskip -\leftskip
     {#4}\nobreak
     \leaders\hbox{$\m@th
        \mkern \@dotsep mu\hbox{\,}\mkern \@dotsep
        mu$}\hfill
     \nobreak
     \hb@xt@\@pnumwidth{\hfil\normalfont \normalcolor }%
     \par}%
  \fi}
\newcommand*\l@sectioninfo{\@nodottedtocline{1}{1.5em}{2.3em}}
\NewEnviron{sectioninfo}{%
    \addcontentsline{ptc}{sectioninfo}{%
    \noexpand\numberline{}\BODY}%
}
\makeatother

\def\PrintContents{%
\startcontents%
\printcontents{}{1}{{\bfseries\Large\contentsname}%
  \par\nobreak\vskip-6pt\noindent\hrulefill}%
  \vskip-6pt\noindent\hrulefill\vskip3\baselineskip%
}

\begin{document}
\tableofcontents

\chapter{First chapter}
\PrintContents

\lipsum[4]

\section{First section of chapter one}
\begin{sectioninfo}
\protect\begin{itemize*}
\protect\item The first important thing about this section.
\protect\item The second important thing about this section.
\protect\item The third important thing about this section.
\protect\end{itemize*}%
\end{sectioninfo}
\lipsum[4]
\section{Second section of chapter one}
\begin{sectioninfo}
\protect\begin{itemize*}
\protect\item The first important thing about this section.
\protect\item The second important thing about this section.
\protect\item The third important thing about this section.
\protect\item The fourth important thing about this section.
\protect\end{itemize*}%
\end{sectioninfo}
\lipsum[4]

\chapter{Second chapter}
\PrintContents

\lipsum[4]

\section{First section of chapter two}
\begin{sectioninfo}
\protect\begin{itemize*}
\protect\item The first important thing about this section.
\protect\item The second important thing about this section.
\protect\end{itemize*}%
\end{sectioninfo}
\lipsum[4]
\section{Second section of chapter two}
\begin{sectioninfo}
\protect\begin{itemize*}
\protect\item The first important thing about this section.
\protect\item The second important thing about this section.
\protect\item The third important thing about this section.
\protect\end{itemize*}%
\end{sectioninfo}
\lipsum[4]

\end{document}

An image of the general ToC:

enter image description here

And some images of the partial ToCs:

enter image description here

and

enter image description here

Remark

The descriptions are provided with a sectioninfo environment; inside this environment fragile comments need to be protected; since itemize* (from enumitem) is used in the descriptions, \begin{itemize*}, \end{itemize*} and \item need a prepended \protect.


Here is how to do it with etoc. I have added a "minitoc" of chapter abstracts, additionally to the tocs of section abstracts, one per chapter.

The update adds a second code sample in response to comments: how to use the method with unnumbered chapters (\chapter*) and how to use enumerate* rather than enumerate for the gathering of section chapters done at the start of each (now unnumbered) chapter.

page 1

abstracts 1

page 3

abstracts 2

page 5

abstracts 3

\documentclass{book}

\usepackage[inline]{enumitem}
\usepackage{etoc}
\usepackage{hyperref}% checking compatibility (also for pdf bookmarks)

\etocsetlevel{chapterabstract}{6}% invisible in TOCs unless level changed
\etocsetlevel{sectionabstract}{6}% invisible in TOCs unless level changed

\usepackage{environ}

%%%%

\NewEnviron {sectionabstract}{%
   \expandafter\SaveSectionAbstract\expandafter {\BODY}%
}%

\newcommand\SaveSectionAbstract [1]{%
   \etoctoccontentsline{sectionabstract}{\unexpanded{\unexpanded{#1}}}}

\NewEnviron {chapterabstract}{%
   \expandafter\SaveChapterAbstract\expandafter {\BODY}%
}%

\newcommand\SaveChapterAbstract [1]{%
   \etoctoccontentsline{chapterabstract}{\unexpanded{\unexpanded{#1}}}}

%%%%

\newcommand\PrintSectionAbstracts {%
    \begingroup
% level must be set *before* use of \etocsetstyle
       \etocsetlevel {sectionabstract}{2}
       \etocsetnexttocdepth {sectionabstract}
       \etocsetlevel {subsection}{3}   
       \etocsetstyle {section}
          {\begin{enumerate}}
          {}
          {\item \etocname:~}
          {\end{enumerate}}
       \etocsetstyle {sectionabstract}
          {}
          {}
          {\etocthename\par}
          {}
       \etocsettocstyle{\subsection*{Section abstracts}}{}
       \localtableofcontents
    \endgroup
}   

\newcommand\PrintChapterAbstracts {%
    \begingroup
       \etocsetlevel {chapterabstract}{1}
       \etocsetnexttocdepth {chapterabstract}
       \etocsetlevel {section}{2}   
       \etocsetstyle {chapter}
          {\begin{enumerate}}
          {}
          {\item \etocname:~}
          {\end{enumerate}}
       \etocsetstyle {chapterabstract}
          {}
          {}
          {\etocthename\par}
          {}
       \etocsettocstyle{\subsection*{Chapter abstracts}}{}
       %\localtableofcontents 
       % better not local, as the main TOC itself, a priori printed before,
       % could have been configured to create a chapter entry in the toc file
       \tableofcontents
    \endgroup
}   

\begin{document}

\tableofcontents % standard table of contents

\PrintChapterAbstracts % chapter abstracts

\chapter{First Chapter}
   \begin{chapterabstract}
        \begin{itemize*}
            \item First this chapter talks about....
            \item Second we have ...
        \end{itemize*}
   \end{chapterabstract}

\PrintSectionAbstracts % section abstracts

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren,
no sea takimata sanctus est Lorem ipsum dolor sit amet.

\section{First Section}

    \begin{sectionabstract}
        \begin{itemize*}
            \item this first section talks about Lorem ipsum dolor sit amet,
              consetetur sadipscing elitr \dots
            \item it also talks about \dots
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\section{Second Section}

    \begin{sectionabstract}
        \begin{itemize*}
        \item this second section talks about ipsum dolor sit amet, consetetur
          sadipscing elitr,
        \item it also talks about sed diam voluptua. At vero eos et accusam et
          justo duo dolores et ea rebum.
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\section{Third  Section}

    \begin{sectionabstract}
        \begin{itemize*}
        \item this third section talks about ipsum dolor sit amet, consetetur
          sadipscing elitr,
        \item it also talks about sed diam voluptua.
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\chapter{Second Chapter}
   \begin{chapterabstract}
        \begin{itemize*}
        \item First this second chapter talks about ipsum dolor sit amet,
          consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut
          labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos
          et accusam et justo duo dolores et ea rebum.
        \item Second we have clita kasd gubergren, no sea takimata sanctus est
          Lorem ipsum dolor sit amet.
        \end{itemize*}
   \end{chapterabstract}

\PrintSectionAbstracts % section abstracts

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren,
no sea takimata sanctus est Lorem ipsum dolor sit amet.

\section{First Section}

    \begin{sectionabstract}
        \begin{itemize*}
            \item this first section of the second chapter talks about \dots
            \item it also talks about \dots
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\section{Second Section}

    \begin{sectionabstract}
        \begin{itemize*}
            \item this section talks about \dots
            \item it also talks about \dots
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\section{Third  Section}

    \begin{sectionabstract}
        \begin{itemize*}
            \item this third section talks about ipsum dolor sit amet, consetetur sadipscing elitr,
            \item it also talks about sed diam voluptua. At
vero eos et accusam et justo duo dolores et ea rebum.
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\end{document}

Remark: this is a further elaboration of my answer to Make a second "table of contents" incorporating a short summary for each section. The new thing is the use of package environ to allow an environment rather than a command syntax. Apart from that this is essentially the same technique.


Update:

page of the main table of contents (notice that it is using the class default reserved spaces for the section numbers, which here is too big as chapters are left unnumbered; you can either use etoc more fully, see the manual for examples, or use for example tocloft to customize this main TOC printed in compatibility mode).

The chapter abstracts are printed using a description environment.

section abstracts II 1

page of first chapter

section abstracts II 2

page of second chapter

section abstracts II 3

\documentclass{book}

\usepackage[inline]{enumitem}
\usepackage{etoc}
\usepackage{hyperref}% checking compatibility (also for pdf bookmarks)

\etocsetlevel{chapterabstract}{6}% invisible in TOCs unless level changed
\etocsetlevel{sectionabstract}{6}% invisible in TOCs unless level changed

\usepackage{environ}

%%%%

\NewEnviron {sectionabstract}{%
   \expandafter\SaveSectionAbstract\expandafter {\BODY}%
}%

\newcommand\SaveSectionAbstract [1]{%
   \etoctoccontentsline{sectionabstract}{\unexpanded{\unexpanded{#1}}}}

\NewEnviron {chapterabstract}{%
   \expandafter\SaveChapterAbstract\expandafter {\BODY}%
}%

\newcommand\SaveChapterAbstract [1]{%
   \etoctoccontentsline{chapterabstract}{\unexpanded{\unexpanded{#1}}}}

%%%%

\newcommand\PrintSectionAbstracts {%
    \begingroup
% level must be set *before* use of \etocsetstyle
       \etocsetlevel {sectionabstract}{2}
       \etocsetnexttocdepth {sectionabstract}
       \etocsetlevel {subsection}{3}  
% enumitem redefinition of \item causes the closing of groups
% hence either some \expandafter, or like here \global saving
% of number and name 
       \etocsetstyle {section}
          {\begin{enumerate*}}
          {\global\let\EtocNumber\etocthenumber
           \global\let\EtocName\etocthelinkedname}
          {\item [{\bfseries\EtocNumber.}~]\EtocName: }
          {\end{enumerate*}}
       \etocsetstyle {sectionabstract}
          {}
          {}
          {\etocthename\par}
          {}
       \etocsettocstyle{\subsection*{Section abstracts}}{\medskip}
       \localtableofcontents
    \endgroup
}   

\newcommand\PrintChapterAbstracts {%
    \begingroup
       \etocsetlevel {chapterabstract}{1}
       \etocsetnexttocdepth {chapterabstract}
       \etocsetlevel {section}{2}   
       \etocsetstyle {chapter}
          {\begin{description}}
          {}
          {\item[\etocname] }
          {\end{description}}
       \etocsetstyle {chapterabstract}
          {}
          {}
          {\etocthename\par}
          {}
       \etocsettocstyle{\subsection*{Chapter abstracts}}{}
       \tableofcontents
    \endgroup
}   

\begin{document}

\renewcommand{\thesection}{\arabic{section}}

\tableofcontents % standard table of contents

\PrintChapterAbstracts % chapter abstracts

\chapter*{First Chapter}
\addcontentsline{toc}{chapter}{First Chapter}

   \begin{chapterabstract}
        \begin{itemize*}
            \item First this chapter talks about....
            \item Second we have ...
        \end{itemize*}
   \end{chapterabstract}

\PrintSectionAbstracts % section abstracts

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren,
no sea takimata sanctus est Lorem ipsum dolor sit amet.

\section{First Section}

    \begin{sectionabstract}
        \begin{itemize*}
            \item this first section talks about Lorem ipsum dolor sit amet,
              consetetur sadipscing elitr \dots
            \item it also talks about \dots
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\subsection{this subsection should not create problems}

\section{Second Section}

    \begin{sectionabstract}
        \begin{itemize*}
        \item this second section talks about ipsum dolor sit amet, consetetur
          sadipscing elitr,
        \item it also talks about sed diam voluptua. At vero eos et accusam et
          justo duo dolores et ea rebum.
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\section{Third  Section}

    \begin{sectionabstract}
        \begin{itemize*}
        \item this third section talks about ipsum dolor sit amet, consetetur
          sadipscing elitr,
        \item it also talks about sed diam voluptua.
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\chapter*{Second Chapter}
\addcontentsline{toc}{chapter}{Second Chapter}

   \begin{chapterabstract}
        \begin{itemize*}
        \item First this second chapter talks about ipsum dolor sit amet,
          consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut
          labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos
          et accusam et justo duo dolores et ea rebum.
        \item Second we have clita kasd gubergren, no sea takimata sanctus est
          Lorem ipsum dolor sit amet.
        \end{itemize*}
   \end{chapterabstract}

\PrintSectionAbstracts % section abstracts

Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod
tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At
vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren,
no sea takimata sanctus est Lorem ipsum dolor sit amet.

\section{First Section}

    \begin{sectionabstract}
        \begin{itemize*}
            \item this first section of the second chapter talks about \dots
            \item it also talks about \dots
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\section{Second Section}

    \begin{sectionabstract}
        \begin{itemize*}
            \item this section talks about \dots
            \item it also talks about \dots
        \end{itemize*}
    \end{sectionabstract}

bla bla bla

\section{Third  Section}

    \begin{sectionabstract}
    \begin{itemize*}
    \item this third section talks about ipsum dolor sit amet, consetetur
      sadipscing elitr,
    \item it also talks about sed diam voluptua.
    \end{itemize*}
    \end{sectionabstract}

bla bla bla

\end{document}