This was my favorite pre-trip reading for Madagascar. Heather Heying is a frog researcher who studied mantella frogs on the island of Nosy Mangabe (my favorite place of the trip). She tells the story of her time in Madagascar on this island, living in a tent. While she did her studies in the 1990's, the island has changed a lot since she was there, largely due to increased tourism.
Her description of the place, the people, and the odd things she discovered about Madagascar was fun to read. This was the only book I read about Madagascar that made me actually want to go there, and I thought she was very honest in her descriptions of both the good and the bad she encountered. If you have any interest in Madagascar at all, I highly recommend this as a good read.
You can read more about the book or order it from Amazon here.