The Book of Hallowe’en (1919) by Ruth Edna Kelley is considered the first book-length history of the holiday, offering a comprehensive overview of Halloween's origins, traditions, and folklore. It traces the holiday's evolution from ancient Celtic rituals to the early 20th-century customs practiced in America and Europe. The Book of Hallowe’en is regarded as a classic for anyone interested in the history and evolution of Halloween traditions and is often noted for its detailed, well-researched, yet charming perspective.