This book is aimed at anyone who is new to Sportives, overall though, its focus is on training for a lengthy sportive which requires a good deal of training and preplanning. I myself have done a number of sportives, but bought this book to help as I was increasing my mileage significantly compared to what I've done before.
There is a good deal of advice at the beginning of the book which should already be known by most Cyclists, aside from perhaps complete beginners. Things like wearing proper clothing, making sure your bike fits etc.
What I found most useful were the stretching exercises which are cycling specific and help with core strength, along with the training plans which they refer to as being a 'menu'. That was quite good because it means if you have commitments that come up and interfere with your training, you can simply choose to do something shorter, which can be just as beneficial. I liked this because it just makes sense. Trying to stick to a rigid training plan is often difficult when you have other things going on and only makes you feel frustrated about it if you miss or have to cut something short.
Nutrition is obviously massively important and the book does a good job of covering how to handle eating and hydration on and off the bike, both during training and the event itself. Don't expect detailed diet plans of everything you should be eating, but then thats a whole other subject and should be self-explanatory.
The small tips and advice from Pros, Team managers etc are all very useful and current so make a worthwhile addition. When you see some of those names, its also quite reassuring that you know you are getting good advice.
The one area I felt the book didn't cover so much was the actual event you have been training for, it was only a few pages. Given that its aimed at people unlikely to have taken part in a major sportive, I expected it to cover a bit more about things like group etiquette, hand signals, working together etc. While it had some brief sentences from people who had finished major sportives, it would have been good to hear a bit more depth about their experiences. I respect the fact though that the book is largely titled getting fit for Sportives, so obviously isn't the main focus.
So in summary, I've found it useful for training and picked up a few things I hadn't thought of before.