This books teaches you vi and Vim in at a very pleasant pace. It does not dive immediately into all kinds of details but starts with historical background on vi. That makes many characteristics of vi all of sudden much more logic. Then it investigates the functionality of vi step by step. It is remarquable how fast one learns vi considering the seemingly easy going pace of the writers. That emphasizes their skill to teach. In the same way Vim is treated. Highly recommended.
I as many others are Vim users. The Vim coverage of this book is really poor and not worth the money. If you, in 2008, still use Vi you might get something out of this book, but the previous Vi book from O'Reilly might be worth considering in stead.
There are other Vim books out there and plenty of internet resources. This book is not worth it. I'm actually surprised that this was published by O'Reilly