I have lots of books, but prefer video instead. I never seem to get around to the books, but will watch video training.
For $25/month, lynda.com offers a thousand hours of training Quicktime movies in many applications, including Photoshop.
I also belong to NAPP, National Association of Photoshop Professionals (photoshopuser.com). For $99/year, you get a wonderful Photoshop User mag which has tutorials and lots of tutorials on their website. There are dozens of discounts which usually pays for the membership price.