Let me start by saying that the only criticism I have of this book is that it doesn't talk about the gorillas themselves, their lives and behavior, all that much. If you want a natural history of gorillas, look elsewhere.
Having said that--this is an excellent book and I highly recommend it, especially if you're going to Rwanda. The book follows the development of the Mountain Gorilla Project from the last years of Dian Fossey's life through the Rwandan genocide and beyond. It is written by the couple who took over the Project after Fossey's murder, and tells their story in fascinating detail. It is a record of the ongoing struggle to maintain a national park in a poor country, of the commitment and hard work of a few people--Europeans, Americans, Rwandans--in difficult and even deadly circumstances, and, most importantly, of the interactions of poverty, politics, personality, corruption, ignorance, education, inspiration, fear, courage, joy and tragedy in the real world of conservation biology.
While this is about one country, one park (mostly) and one species, it will give the reader a much clearer understanding of the diffculties faced by field biologists, park rangers, conservationists and governments the world over who are trying to preserve wild places.
The book is written in a lively, conversational style and makes every effort to be even-handed with some difficult personalities (Fossey's not least of these). Even though the book devotes only a chapter to the horror of the genocide, it presents the events in both a larger context and very personal, affecting detail. In fact, one of the great strengths of the book is its graceful incorporation of the big picture and the snapshot to tell a whole story.
If you're going to Rwanda (or if you've been there)--BUY THIS BOOK!