I have Photoshop CS3 for Digital Photographers by Scott Kelby and I liked it. It shows you specific steps to accomplish a given task. You like Scott Kelby or you don't. The only thing I that bothered me, was that I didn't know why he was doing things one way or another and decided I needed a more basic book.
So I bought a book called Photoshop CS3 for Dummies, by Barbara Obermeier. It is organized as 9 mini books, with a book dedicated to specific topics such as Selections, Layers, Channels, Retouching, Printing and so on. It's a long read, but I know a lot more about what I'm doing now, and its a great reference book.