Tsunojima, Aoyashiki's burnt down remains and a decagon-shaped guesthouse. The latter is used by seven students from a university's mystery club and as someone would naturally expect considering this setting, serial murders start happening on this otherwise uninhabited island with no one willing to confess the crimes. Two other students who did not visit the island with their fellow students receive mysterious letters from Nakamura Seji, the proprietor of former Aoyashiki and the whole island, who supposedly died in the incident in the mansion half a year ago. They find out that those letters were also sent to their meanwhile absent fellow students and they begin investigating the incident of Tsunojima's past...
Reading a book with a premise like this does not provide you with anything ingeniously fresh and innovative from today's point of view. However what constitutes the standard of the genre nowadays was heavily influenced by this book and the series that followed. 20 years ago, in a time where mystery as a genre was gradually loosing its key factors and becoming less accurately defined, a mystery maniac called Ayatsuji Yukito began his career as an author. With this debut work as the first volume in his famous yakata-series that is being paid homage to nowadays quite frequently, his approach was a challenge on Agatha Christie's "And Then There Were None".
Retaining the classical setting and atmosphere close to vanishing from the genre in favor of more simple and realistic cases fitting the current circumstances, he was also aware of this romance versus realism difficulty. I guess I cannot go into detail without spoiling, but he gave his work a sense of realism by also focusing on the parallel plot line on the mainland, which is one of the most significant differences to Christie's novel. The other, which also is another important factor in the shinhonkaku movement, is that he is well aware of the gap between the founders/foundations of the genre and his own work and therefore, being the mystery maniac he is, weaves lots of meta-references into the setting and dialogues, signalizing the conclusion of the important base of the genre and also the beginning of its new era from now on. The genre in the genre, the 'nesting' mystery complex, so to speak. 1987, when this book's publication started, this actually was a new development and many orthodox mystery maniacs did not feel comfortable with it. On top of that apparently there was a notion called 'honkaku bashing' which kind of startled me seeing how this new stage of the genre became so popular over the years. Of course Ayatsuji was walking a fine line back then since the key factors of the genre were already established so deep-seated and some fans could not deal with the partial demystification of what they cherished so far.
Regardless of the literary importance of this work, any mystery fan who became a fan after this development back then should definitely be able to thoroughly enjoy this book. Despite being a debut work I felt like there never was a point were the plot did not move forward steadily and while the revelation at the end was not that surprising in itself, the brilliant structuring and herrings actually succeeded in hindering pulling all the threads for the whole picture together for myself. While the characters are not anything flashy or intriguing for themselves, what they talk about catches the interest of any mystery fan. In a maniac's way. You'll see what I mean, I don't think there are that many novels out there that are so meta in spite of being so orthodox at the same time. Well, Ayatsuji's works are what any kind of meta detective fiction was built upon in the following years after all.
Be sure to get the remodeled, revised, whatever bunko edition since Ayatsuji made some minor corrections and kind of adjusted the overall style. According to him those changes are really minor though and did not change the original text to a significant extent. Following his afterwords for the new edition (which he also points out as the definite, official version of the novel btw) are commentaries and explanations concerning the shinhonkaku movement and jukkakukan no satsujin in particular, contributed by honkaku writer Ayukawa Tetusuya and mystery critic Togawa Yasunobu, which can be fairly interesting if you are interested in mystery as a literary genre and... the chatter of old maniacs.