Keller's work sets a new standard for Kantian scholarship. This book is so thorough that it demands an intensive reading and much thoughtful reflection to fully grasp Keller's insights. If you want to understand Kant's transcendental philosophy in a way that Kant would probably appreciate, buy this book. If you want to understand the significance and rigor of transcendental idealism in Fichte, Schelling, or Hegel, this book will give you a clear foundation to build those studies upon. Compared to Guyer and Allison, Keller has established a new standard that will eventually have to be addressed by the old guard.