This book offers a gentle introduction to Hex, the classic board game created by Piet Hein and popularized by John Nash and Martin Gardner. The first three chapters cover rules, basic strategy, and history. The remaining eight chapters cover a variety of topics: mathematical properties (there are no draws, the first player can win, the acute corner is a losing first move), the related game of Y, winning strategies for small boards, how computers play Hex, an analysis of Random-Move Hex (where one or both players move randomly) and Dark Hex (the imperfect information version of the game, where you can't see your opponent's moves). Did we mention puzzles? There are puzzles in every chapter, with solutions.This book is intended for anyone interested in playing board games or learning some recreational mathematics. It is written for a wide audience and will be enjoyed equally by general readers and professional mathematicians. The book could be used as a textbook or companion resource for a topics course on recreational mathematics or game theory or as a source for undergraduate research questions.