Book excerpt: Tracks and Shadows is both an absorbing autobiography of a celebrated field biologist and a celebration of beauty in nature. Harry W. Greene, award-winning author of Snakes, delves into the poetry of field biology, showing how nature eases our existential quandaries. More than a memoir, the book is about the wonder of snakes, the beauty of studying and understanding natural history, and the importance of sharing the love of nature with humanity. Illustrations.