It's the mystery William James called "the darkest in all philosophy": "[W]hy is there something rather than nothing?" For Jim Holt, it is a question that may never find an answer, but one endlessly worth asking. In this highly engaging book, Holt visits great thinkers in mathematics, quantum physics, artificial intelligence, theology, philosophy, and literature. These conversations don't lead him toward any conclusion, but they make for a lively, thoughtful read, whether your worldview tends toward Spinoza (in which "reality is a self-sustaining causal loop: the world creates us, and we in turn create the world") or like Stephen Hawking, still searching for the final theory of everything. Holt is a generous guide, laying out a brief history of how philosophers have approached these questions before bringing us along on his tour of modern thinkers-some of whom are also fairly eccentric, hilarious talkers. The author's willingness to include his personal struggles with being and nothingness-as when he faces the death first of his dog, then of his mother-grounds the book in intimate, humane terms. We may never know why the universe exists, but we know how to grieve those who exit it.