Books on Photoshop?

I like:
• "Photoshop CC 2015 Classroom in a Book" for an all around review of all the basic features

• "Adobe Lightroom and Photoshop Classroom in a Book" for integrating Adobe Photoshop with Adobe Photoshop Lightroom

• "Adobe Photoshop for Photographers" by Martin Evening for using Photoshop as a photographer (as opposed to a designer)
• "How to Cheat at Photoshop" by Steve Caplin for cool tips and tricks in using Photoshop

• "The Photoshop Workbook" by Glyn Dewis for retouching and compositing cool tips and tricks
• Any of the "Master Class" books for advanced techniques.
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If you have particular interests such as retouching, restoration, compositing, design, Web, Interface Design, etc. or wish to focus on a particular aspect of the program such as Brushes, Filters, Camera Raw, 3D, Type Effects, Photo Effects, Blend Modes, Layers, Adjustment Layers, etc. then there are also excellent books targeting those specific areas. 
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I still find older Photoshop books to be useful as well as they highlight useful techniques that are not commonly taught today. I still pull out "Channel Chops" by Bert Monroy (one of the very first books on Photoshop) for help with Channels and Calculations.
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When buying a computer book, I like to go to a bookstore and open the actual book and examine it. One thing I check for in a computer book is how easy is it to find the material I am looking for. If I can't find the material I want, the book is of very limited use to me.
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Hope this is helpful and good luck!

It really depends on what you want to with Photoshop. The Classroom in a book series is fine for all around general stuff. Personally I prefer the Photoshop Down and Dirty Tricks by Corey Barker as that type of stuff there is what I do mainly. Another is the Master Class Advanced Compositing in Photoshop by Bret Malley. I also do restorations and there is a couple good ones for that as well.

So really it all comes down to how you use Photoshop and what you want to learn.