"The Book of Three" is a fantasy novel written by Lloyd Alexander. It is the first book in the "Chronicles of Prydain" series, which consists of five books in total. The series draws inspiration from Welsh mythology and follows the adventures of a young assistant pig-keeper named Taran. In "The Book of Three," Taran embarks on a quest to stop the evil Horned King from obtaining the mystical Black Cauldron, which has the power to raise an army of undead warriors. Along the way, he is joined by various companions including the wise yet eccentric enchanter Dallben, the princess Eilonwy, the bard Fflewddur Fflam, and the creature Gurgi. The novel explores themes of heroism, friendship, and the struggle between good and evil. It has been praised for its engaging characters, rich world-building, and adventurous plot. Lloyd Alexander's work in the "Chronicles of Prydain" series has had a significant influence on the fantasy genre and has garnered a loyal following since its publication.