First published in January 1996, Devlin's Angle is a popular online monthly feature on the MAA Math Values website. In this book, Keith Devlin has celebrated the first quarter century of the MAA's web presence by curating a collection of 46 of the 288 posts from that period, chosen for their relevance to K-12 mathematics teaching. The posts are organized into nine themed chapters, each beginning with its own introduction regarding the history and nature of the posts presented. Topics covered include the teaching of multiplication, teaching for conceptual understanding, and a discussion of mathematical creativity. The book closes with a final chapter touching on teaching at the college level. Due to the nature of mathematics, many of the columns contain observations that remain relevant in the present day. Devlin's lively, conversational style is encapsulated in this informative and thought-provoking collection. It will appeal to mathematics teachers at all levels, as well as anyone interested in mathematics education at the K-12 level.