I've just borrowed a new book from the library called Googlepedia. It describes how all the various Google apps work and has lots of useful tips. It has also some good background to why Google has succeeded. The author, Michael Miller, admits that writing a book about anything on the net is like shooting at a moving target and a book about Google would seem to be a very swift target to aim at. To keep things up to date he also runs a blog on the subject.
The book is well worth looking at as long as you realize that it will be at least partly out of date by the time you finish it (weighing in at over 700 pages), thus making it a good library loan but a bad idea to buy someone as a birthday present. An admirable project though I'm sure the legendary figure of Sisyphus would have sympathised with the author.
Books on IT tend to be weighty objects and have a very short shelf life. We all have copies of mega-sized guides to, say, Windows 95 or Java programming for dummies lurking somewhere on the shelves helping to prop up other less bulky publications. Despite all the on-line guides and FAQs we still seem to need the reassuring hard copy. However, it is rather a lot of paper for something so ephemeral.