It's updated. The website does have a LOT of information, but it's worth buying the book IMHO becuase some of the website's info is dated and he's done a great job of updating the book. Besides, it's a lot easier to read the book on the crapper.
What kind of in-depth info are you looking for? At some point, you may want to look into Designing Great Beers, or Noonan's book, or several others, depending on what kinds of information you are looking for.