The Decagon House Murders is a Japanese mystery novel by Yukito Ayatsuji, first published in 1987. The book is often considered one of the best examples of the “honkaku” (meaning “authentic”) mystery genre, which emphasizes the use of logical puzzles and clues for the reader to solve the mystery alongside the characters.

The story follows seven college students who travel to an isolated island to spend their summer vacation in a strange house called the “Decagon House.” The house was originally built by a wealthy and eccentric man, but it has been abandoned for years and is rumored to be cursed. The group soon finds themselves trapped on the island when a storm hits, and they begin to experience a series of gruesome murders, with each victim killed in a manner that mirrors the deaths in a classic mystery novel.

The novel is structured in a unique way, with the first half of the book consisting of a series of diary entries from the seven college students, which provide insight into their personalities and relationships with each other. The second half of the book is a more traditional mystery narrative, as the remaining characters try to solve the murders and identify the killer. The book is known for its intricate plot, complex characters, and clever use of literary allusions and references.

The Decagon House Murders has been adapted into various media, including a manga series and a live-action film. The book has also been translated into multiple languages and is considered a classic of Japanese mystery literature. You can get a copy of this amazing book from Amazon here.