I agree with Stamper that Michael Kieran's book is good and its content is valid for everything it teaches using any version of Photoshop from the time it was published, and some time before that.
Newer books are backwards compatible to previous versions of Photoshop except for the content that explains the use of new features which weren't available when the book was written.
As successive versions of Photoshop bring new and improved ways of editing images, there are older techniques which become replaced with better and easier ways of doing essentially the same thing - and often more.
While the really classic titles survive successve versions of Photoshop, you do sometimes need the newer books to get on top of the new features in the new versions. But, as I mentioned yesterday, there is also a plethora of free resources on the internet.
As a footnote, I really like the way Ben WIllmore handled the process of up-grading books with versions of Photoshop. Since his CS Studio Techniques book, he authored two slim up-date books at much lower price targeted specifically on the new features of CS2 and CS3. He also wrote a CS3 version of Studio Techniques for those who want everything under one roof, but the slender up-grade approach remains most welcome. By the way, for Anders, with a specific interest in more effective color work, Ben also authored a set of two DVDs called "Mastering Color" published by KW Computer Training, available through NAPP (National Association of Photoshop Professionals), at NAPP
. Highly recommended for your purposes.