Kant's Critique of Pure Reason is difficult. Most people will need a guidebook to achieve an adequate understanding of this profound work. In my attempts to read it I took the approach of reading until I felt my understanding was becoming less than adequate, and then started reading the secondary literature. I started reading the secondary literature after reading the first sentence! Gardner's was one of the first I started to read, but quickly gave up because this book is as difficult to read as Kant. Fortunately, I did not give up but eventually found the one piece of secondary literature I needed -- "A Kant Dictionary" by Howard Caygill. Even more importantly, I found a forgiving translation (Pluhar's) which is blessed with a superb introduction. Even with these aids, Kant is very difficult, and the reader or student is not helped by convoluted, over-complicated texts like Gardner's. So although I found a couple of paragraphs in Gardner useful, I cannot give it more than one star because it fails in the main aim of a guidebook. A guidebook should help the inexperienced reader, not make the severest demands on his or her philosophical understanding. So reader beware, and use the "look inside" feature to its full extent before thinking of buying.