I have an earlier book and would recommend it. Does what it says on the tin, i.e. it focusses almost solely on the features or most use for photographers.
I also have earlier versions of Photoshop Classroom in a Book, and unless there's info to suggest the CS6 version is somehow less good than the others, that's also worth a look. It goes into all the features, not just those of use to pure photographers, which may or may not be an advantage to you.
Check out Lynda.com. Generally the tutorials there are very good to excellent.