The book has excellent overview of Bodyweight exercises but I find the workouts plans are far too complicated to stick to. It feels like you need a cheat-sheet to work out what exercises and what style of workout you need to do on any given day. In part this is because all the workouts are named after mythical creatures instead of called by a sensible name like "upper body circuit". In this respect I think You Are Your Own Gym is a better book, as that book has really straight forward workouts that change every few weeks to keep things fresh but never bog you down in endless changes or confusing systems.
There are a few other reasons why I think You Are Your Own Gym is a better book, for example I much prefer that it lays out exercises by body part rather than difficulty, which makes it easy to substitute exercises if you have an injury or space consideration. In this book everything is laid out by difficulty, meaning it might not be entirely obvious what to substitute an exercise for (except for the harder version of the same thing found in the next difficulty section).
This book does have some advantages like better pictures and being in full colour. But If you were only to buy the one book I'd say put your money towards You Are Your Own Gym. I think people will stick to the exercise routines for longer in that book.