What Is Relativity? is a well-written and uniquely readable book that beautifully serves as an introduction to special and general relativity. Jeffrey Bennett carefully avoids bombastic statements and 'spectacularization' of the subject, sticking with well-established facts and presenting them in a clear and compelling manner. -- Alberto Nicolis, Columbia University Since it first appeared more than a decade ago, I have used Cosmic Perspectives by Jeffrey Bennett and his colleagues in no small part because of the excellence of its chapters on relativity. It is wonderful to now have a stand-alone volume in which his lucid, explanatory text and figures are coupled with a thoughtful commentary on why relativity is important in constructing our scientific and personal views of space and time. -- David J. Helfand, President, American Astronomical Society, and President and Vice Chancellor, Quest University Canada I have read lots of introductions to relativity, but none is as clear and compelling as this one. For anyone who is keen to grasp the fundamentally simple yet non-intuitive ideas of both special and general relativity, Jeffrey Bennett's book is the way to go. Impressively understandable and interesting. -- Seth Shostak, Senior Astronomer, SETI Institute ...Bennett's fun book shows readers what relativity means, and what it reveals about our universe. Publishers Weekly For in its relatively few pages, Bennett explains relativity to ordinary readers... An impressively accessible distillation of epoch-making science. Booklist (starred review) A sober, comprehensible account of what every intelligent layman should know about space and time. Kirkus Reviews ... [P]erhaps the best homage that anyone can pay to [Einstein] for such a groundbreaking contribution to physics in particular and science in general. BrainDrain Bennett... has written an entertaining, brilliant introduction to Einstein's ideas... that is impressively understandable. CHOICE