I've found this to be extremely useful, it covers topics from colour management and calibration, through masking techniques, noise reduction, star control, LRGB and channel mixing, mosaics and sharpening all the way through to preparing your images for print or digital publication. A very in-depth book that explains processing in easy to follow steps with a CD of example images provided for you to practice with.
It's quite hard to find these days, try Kieran at SCS Astro - that's where I bought my copy from a couple of years ago.
ISBN: 978-0-943396-85-9