Purchase this book if you need in-depth knowledge in the area of sleep medicine. Online access to the book and periodic updates are a good idea and are available with one version of the book. There have been a significant number of updates over the last two years. There is additional information on the web site beside the text. Some can be found elsewhere, e.g., practice parameters from the AASM, but it is nice to see it gathered in one place. One disappointment is the Atlas of Sleep Breathing Disorders of which half of the pictures and graphs haven't shown (broken links) for months. The Pocket Consult (ne MobiPocket Reader, which is included as a download) is useful and allows downloading text excerpts (no tables or graphs) from the book to a PDA for reference on the road. Addendum -- if you click on the Printer Friendly tab while in the Atlas of Sleep Breathing Disorders it will bring up a second window with the pictures and graphs where they should be.