I can highly recommend Photoshop Astronomy, Alexander. Mine is starting to get a bit dog eared
Another one you might want to consider, especially if you get into dedicated CCDs that use MaximDL or CCDSoft is Wodaski's "The New CCD Astronomy". It is also a very good book with great directions from equipment selection, setting up, processing and other skills.
http://www.newastro.com/newastro/default.asp
I can't recommend "The Zone System" though. Great information but not value for money IMHO.