This book appears to be the first book about training with a powermeter and seems to be the standard. The concepts developed by the authors are referred to by many other books and training tracking software (e.g., Garmin's Connect web site). A more scientific quantified approach is taken, which I like a lot. Limitations on the existing body of knowledge are mentioned honestly, too. This new second edition was updated with a chapter in particular for triathlon. Since I am a triathlete myself, I really appreciate that. Otherwise, the book is targeted more towards pure cyclists. In triathlon, there is never any true sprint, so not everything covered by the book is relevant to a triathlete. The authors refer every now and then to the software they developed and sell. The charts produced by that software and shown in this book are, however, general enough and provided by other software (such as the free Golden Cheetah), too. Overall, I found this book very helpful and convincing. I will try to follow the proposed approach in my preparation for the coming season.
One note about the Kindle version (which I bought): The charts and tables are extremely small. I cannot read them without glasses (you almost need a lense) and the Kindle software does not allow one to zoom in. I would not recommend to buy the Kindle version.