I bought this book many years ago and have used it so often it is untrue. The lay out is easy to understand and the stones are grouped logically, with everything from crystal formation to MOH hardness to chemical formula. I would recommend it to anyone with an interest in gemmology, as it contains the detailed information for professionals, as well as plenty of information for the enthusiastic amateur. In short it's a comprehensive reference book that I keep turning to again and again, and though I have other gem books, this one is all you need. If you're going to buy a gem reference book, buy this one.