You need to understand RAW mode to get the most out of your digital photos. The fundamental reason is that they contain more editing headroom. By shooting in RAW, you can ignore all the camera settings other than ISO, exposure and shutter. This book also explains the linearity of camera sensors versus the non-linearity of our perception, which is why you want to expose as close to clipping highlights as possible. All of the other corrections are done by the camera to the RAW image, including sharpening, contrast and brightness control, noise reduction, spectral correction, barrel/pincushion distortion correction, color correction (tint, saturation and especially white balance), etc. etc. This effectively means I can ignore 90% of the menu options on my camera and only worry about exposure.
For me, the RAW converter can grab an extra stop of highlight detail over Canon's in-camera converter (EOS 5D) and does a better job at noise reduction. That alone is worth shooting in RAW.
I came to this book after seeing it recommended in Martin Evening's "Photoshop CS2 for Photographers" (an absolute gem) and the Adobe classroom in a book (a dud). Like Evening's book, this one assumes you're serious: you have print or web customers, need to calibrate color, need to archive, and want to automate as much as possible yet still retain creative options. Most of it's about gamma (digital's Zone System for contrast and highlight/mid/shadow detail) and color correction.
I found this book to be rather repetitious and far too filled with rah-rah-RAW prose. An even bigger chunk just walks you through the menus, buttons, etc. The remaining bit is worth the price of admission -- it tells you how to understand the conversions and then set up your workflow for the best balance (for you) between automation and creative control. I also like that it's written for photographers; if you don't understand histograms and gamma, this is probably not a good starter book.
Ironically, the images in this book are horrible. They're about the size of medium format transparencies (60mm or 2 1/4 inch square). I couldn't tell the difference between most of the compare-and-contrast pairs. Nor could my wife. The other drawback is that it's another Photoshop book that's being sold by the pound -- heavy paper, huge font, and very wide margins. Please make the pictures bigger next time.