CIFS mount through fstab not mounting at boot

Have you tried adding the option _netdev to your fstab entry? You would add it with the other options in your string like so

//192.168.0.26/mythtv/media  /media/mybooklive  cifs  username=user,password=pass,_netdev,umask=002,uid=136,gid=144,iocharset=utf8   0       0

_netdev is supposed to delay the mount until after the network connects.

if _netdev doesn't work, try the option:

x-systemd.automount

instead. It works by mounting the drive at first access.

To test the automount, unmount your share if it's currently mounted:

$ sudo umount /media/mybooklive

And then restart the remote-fs systemd unit:

$ sudo systemctl daemon-reload
$ sudo systemctl restart remote-fs.target

I am using the Raspbian-Stretch build dated 2017-09-07 and experienced the same issue. However, I was able to overcome this by going into raspi-config and under the Boot Options menu, I enabled the "Wait for network at boot" option.