Useful books to master Salesforce

I own the first and last book and I can say they are completely worth it! I learn a lot thanks to them and improved a lot my coding skills and overall knowledge of the salesforce platform. I would totally recommend those!

Another book I also bough recommended by a Friend was Clean Code, although it's not salesforce related can be applied to any coding language.

I was lately considering this one would like to know opinions if it's worth: Apex Design Patters

While I love books, I think that they may not be the best way to improve your salesforce skills unless you've already exhausted the huge variety of free resources, such as:

• Automation Champion
• Trailhead
• SFDC99
• The Official Documentation
• This Udacity Course
• Training videos in Help & Training if you're a premium customer
• Dreamforce videos

The problem with books about the Salesforce platform is that they become out of date so fast and you can typically find the same information for free.