Well...you don't learn nothing from big, leafy books. And Photoshop is one of those things that you can learn without that books. You just have to try some new stuff and do whatever you can think of, and, of course, try to do some stuff after tutorials. They help you very much to learn and understand the principle of the program.Of course, this doesn't mean that anything can be learned by this way. For example, you can't learn any programming language trying new stuff because you don't have any base.