This book delivers a quantitative account of cosmology, designed for a nonspecialist audience. The author outlines basic principles using simple math and physics, but still provides rigorous models of the universe. He offers an ideal introduction to the key ideas in cosmology, without going into technical details. The approach used is based on the fundamental ideas of general relativity, such as the spacetime interval, comoving coordinates, and spacetime curvature. The book provides an up-to-date and thoughtful discussion of the Big Bang and the crucial questions of structure and galaxy formation. The author also briefly discusses questions of method and philosophical approaches in cosmology. Advanced undergraduates in either physics or mathematics will benefit greatly from this book, either as a course text or as a supplementary guide to cosmology courses.