With his landmark 1998 paper [7], Robin Forman launched the study of "Morse theory on cell complexes." The subsequent two decades have seen a tremendous burst of related activity, leading to applications in topology, combinatorics, and data analysis. Now that this discrete Morse theory has matured into an object of study on its own, book-length treatments are beginning to appear. Discrete Morse Theory, by Nicholas Scoville, is an excellent introduction to the subject. In this review, we take a tour through classical smooth Morse theory, introduce Forman's discrete version, and discuss Scoville's contribution.