Peff's (as Kurasaki is more widely known as) book is a great journey through Reason's deeper mysteries for those who have cut their teeth on the virtual studio software and want to see just how deep the hole goes.
Beginners need not apply - read the very good documentation that comes with Reason first - but intermediate level users who have a song or two under their belts and know their way around Reason's virtual rack will find a wealth of information and techniques that will prove indispensible in their later music projects.
Organized like a sort of 3000-level college laboratory class where the subject is Reason, each chapter of the book opens with theory explaining the chapter's topic (CV Routing, Reverb, Redrum Techniques, etc.) and then dives headlong into 15-30 minute hands-on exercises designed to illustrate the various techniques you can use to milk more of Reason than you ever thought possible. By the time you finish this very in-depth, well organized class, you will be able to do a great many, very wonderful things.
Be careful, though. Many of the chapters build on lessons contained in previous ones. For example, many of the chapters dealing with effects such as Filter Techniques assume you have read the chapter on The Combinator, because most of the intricate filter effects you create will be housed within Combinators for easy access. Don't expect to jump in halfway and immediately understand perfectly everything that's going on. But of course, this should be self evident.
Also, beware that this book will give you great powers. With great powers come great responsibility. Please do not use what you learn in this book for evil.