There are two reasons this didn't get four stars. First, with a primary text and two commentators there's a lot of repetition. Second, it's a little dry. The Dalai Lama has since become a much better writer. This book is not for beginners or people looking for the sensational. It is a serious discussion of tantra that demands concentration. Hopkin's supplements contain a nice summary of the doctrine of emptiness, as well as some very handy diagrams of the relationships among Buddhist schools on the issue and even a diagramatic outline of the primary source text. All of this is beneficial for a reader who already has some familiarity with the topic.