MizzBia - 6:44 am on Oct 15, 2008 (gmt 0)

I think the "classroom in a book" series is probably your best bet. Its written by the Adobe Creative Team so you can be sure it will be the most thorough, accurate book. If you go with this series, you will need to get the book that corresponds to the version of photoshop you have. If you have the latest version, CS3, you can buy this book: [amazon.com...]

If you have an earlier version, like PS 6 or 7, you will need to search for a different edition. The dummies series is also very good for beginners and usually breaks things down in a pretty easy-to-learn fashion but I have not personally read one for Photoshop so I cannot attest to its content. If you're interested in those, you can check out these listings:
[amazon.com...]

There are probably hundreds of other good ones to choose from... just make sure to read the reviews before buying.
Good Luck!