The book presents adapted retellings of Celtic hero tales for young readers, focusing on the legendary leader Finn MacCool and his band of warriors, tracing his birth, boyhood, claims to leadership, and many adventures including contests, battles, and encounters with giants and fairyfolk. It intersperses explanatory material about Irish myth, the oral transmission of folk tales, and editorial choices made to combine versions and omit material unsuitable for children, while acknowledging scholarly collectors. The arrangement follows a largely chronological sequence and emphasizes wonder, heroism, and the magical elements of the tradition.