This is a book review of The Cosmic Zoo: Complex Life on Many Worlds by Dirk Schulze-Makuch & William Bains. This book is more about biology than astronomy. There is of course a long history of trying to estimate the number of planets which could support a technological civilization (the topic of this book---not intelligent life in general, though the probabilities of various types of life, including intelligent but non-technological life, are discussed), going back at least to the Drake equation. This book looks at the terms in that equation (which, however, is not mentioned in the book; neither is Frank Drake) in more detail, especially the biological ones. The book opens with two chapters discussing "The Cosmic Zoo Hypothesis", the "Cosmic Zoo" referring to a universe in which life is common. Most of the astronomy is in the second chapter, concerned with the number of habitable planets and so on, as well as a summary of the second part of the book. The bulk of the book, the next nine of the 13 chapters, is concerned with "Major Transitions in Earth's Life History". The last two chapters ask the question "Are There Visitors in the Cosmic Zoo?", discussing ways to test the Cosmic Zoo hypothesis and speculations on what, if anything, the "Great Filter" is, which might make the evolution of technological civilizations difficult. I enjoyed reading the book. The authors obviously know their material well and, except for mistakes which could have been corrected by better proofreading, the book is generally well written.