While not comprehensive, this book is a concise "...introduction to the basic terms found in the major schools of Indian Philsosophy." (From the Preface) I find this statement to be true. As a quick reference this book is very helpful. It contains most of the terms of Indian Philosophy one would need to know, and in many cases it provides a multiple definitions. Sure, some definitions seem simplified, but that is due to their nature, the limitations of the English Language and our own Philosophical Concepts, and to the scope of the book. Dr. Grimes clearly states the aim of the book in the Preface. It is to define "...most terms", and to do this in a 440 page paperback one needs to be brief. Presumably Scholars of Sanskrit and Indian Philosophy should have other References to consult, but I think it still is helpful also to them, because it is easy and quick to use. Sanskrit Students will also benefit because all terms are given in the Devanagari Script and in Romanized Transliteration. I use this book and recommend it.
It helps me to find a translation of certain spritual sanskrit terms. If different schools hold a differnt meaning for the term, the meanings are listed separately for each school. It has to be said that if one would want to find really everything, one would have to buy Monier Williams super large sanskrit english dictionary. However, for a spiritual reader like myself, Grimes book is just great.