I really like the Photoshop WOW series of books. I haven't looked at Photoshop CS for Dummies so I don't know. I wouldn't buy the Photoshop CS Bible unless you know for sure that you are very serious about using photoshop.

Wow series is good
another would be How do Everything With Photoshop CS

You know, if you need some help, there are thousands of photoshop tutorial sites out there

this is a very good tuts page.
http://www.pixel2life.com/tutorials/...Photoshop/All/

Unless you need to have a book to take with you for convenience, I would suggest to look up what you need online. There are tons of free resources for learning just about any software.

If you are a visual learner (like I am) then I would suggest linda.com. There is a fee, but it's not too much and the tutorials are outstanding.

Photoshop 7 ME + Fireworks ..

A book series I'm fond of is the Adobe Classroom in a book. They are about $40 written by Adobe. Who would know the program better than them. in addition I think it is well written and easy to understand.

All people are created different. I stress in classes I teach to learn 1 part of a program. make sure you understand it. Go to the book store and read about that portion of the program in the books there. Whichever books makes the most sense to you is the book for you. Don't take other peoples words on whether a book is good. You probably learn differently from them.