I was lost until I was told about http://www.photoshopuser.com/. The site has some free information, but I joined, ( I think it is $99 a year) and worth every penny. They send out several publications a year to members, there is online help, tutorials, etc. I finally have a basic understanding of Photoshop and the ability to improve.

Another site is http://www.planetphotoshop.com/ but I do not know much about it

To answer your question, I have several books on Photoshop, but nothing that compares to the web site.