Physics got its start with people looking toward the heavens and trying to make sense of the cosmos, and many of the greatest mysteries in modern physics still lie along that distant border. Books that try to explain this are quote popular, and a recent one is Paul Halpern's Edge of the Universe: A Voyage to the Cosmic Horizon and Beyond. In this book, Halpern discusses a wide range of topics, from well-accepted science concepts like the Big Bang theory to more exotic ones like whether it might be possible to create a bridge to other parallel universes. The book contains a lot of speculation, to be sure, but this isn't a case of Halpern trying to promote his own pet theory, but rather an attempt to show how broad the inquiries are that are taking place within the field of cosmology and astrophysics. Anyone who wants to understand what could possibly lie on the limits of our universe would find this book to be a welcome starting point.