Scott Kelby is kind of like the Rachael Ray of photoshop teaching. There are some sound basics in there, but to find what's worthwhile you have to sort through one of the worst senses of humor in publishing and his constant "now you're doing it like the pros" approach.
Martin Evening's books are well written, are much more in-depth, and will give you the all-around knowledge you need to start using PS compentently. If you can wait, Jeff Schewe and Martin Evening have a new book coming out soon as well.