Philosopher and author David J. Chalmers makes an ambitious, daring attempt to expand the understanding of consciousness. Although he admits that his sympathies are with materialism, he concludes that materialist (physical) explanations cannot account for the existence of consciousness. His theory of consciousness is based in the natural world, but he proposes that consciousness has both physical and nonphysical properties. He suggests that a set of psychophysical laws are needed to explain the how and why of consciousness. Although parts of this book are densely technical and call for readers with a thorough background in mathematics, physics and philosophy, Chalmers has taken pains to make his material as accessible as possible to the average well-educated person. He even puts asterisks beside sections that lay readers are likely to find too daunting, and notes those sections general readers might most productively read, skim or ignore. We suggest this book to well-schooled readers who are interested in the philosophy of the mind, cognition or psychology.