Scott Kelby remains the gold standard among authors who write about digital photography software. I have been a fan of Adobe Photoshop Lightroom for a couple of years now, and a user since it's first release. It is by far the best photo software I've seen, in large part because Adobe has managed to include all of the features a digital photographer needs for 99% of his work, and stripped away everything else. Most of the functionality is straightforward, but a few of the controls are subtle and non-obvious if you are not a professional.

Kelby's exposition is, as usual, apt, accurate, and easy to follow. He highlights everything you need in a typical workflow and points out lots of tricks to make it go more quickly. His chapter introductions are as corny as ever, but I've learned by now to just skip them. If you use software for digital photography, buy the Scott Kelby book that goes with it.