I found a great book on masking and compositing called (not surprisingly) "Photoshop Masking & Compositing" by Katrin Eismann at the local Barnes and Noble. This book rocks!
I collect text books on any subject that interests me as I'm an avid reader and researcher, and this one blows away anything else I have. If you are still learning about these two subjects, I highly recommend it. The author has some of the most sensible explanations and demonstrations of the photoshop tools that I've seen yet, and she goes into great detail. Just thought I'd share.