The Devotion of Suspect X

Yasuko kills her violent ex-husband in her Tokyo flat, helped by her daughter. Her neighbour Ishigami, a brilliant and isolated mathematics teacher, hears it through the wall and offers to handle everything.

The police investigation is led by a detective whose university friend Yukawa, a physicist, recognises Ishigami as a contemporary who was once the most gifted mathematician of their year.

You are told who did it almost immediately. The mystery is entirely how it is being hidden.

Devmark’s reading — not a quotation from the book

This is an inverted mystery — a howcatchem rather than a whodunit — and the pleasure is watching two exceptional minds work against each other with the reader positioned between them.

Higashino plays fair. The concealment is a genuine logical construction, and the revelation depends on recognising an assumption the reader has been making rather than on new information.

The solution turns on an assumption you were invited to make, not on a fact you were denied.

Devmark’s reading — not a quotation from the book

The title is the subject. Ishigami's act is not romantic in any conventional sense and is closer to the way he approaches an unsolved problem: total, solitary and indifferent to cost.

The book is also quietly about wasted ability, and about two men who took different routes out of the same talent.

It won the Naoki Prize and is the third Detective Galileo novel, though it stands alone and is the usual entry point.

It is short, cold and precisely constructed, and it belongs with the inverted-mystery tradition rather than with the psychological thriller the cover often suggests.

The reader watches the killing and the cover-up in the opening chapters. The question is never who or how but whether the scheme will hold, and the novel is constructed as a contest between two intellects with the reader in possession of one side's information and not the other's.

You see the murder happen. The mystery is entirely about the arrangement made afterwards.

Devmark’s reading — not a quotation from the book

The neighbour who constructs the alibi and the physicist who helps the police were university contemporaries who recognised each other's ability. Higashino uses the friendship to keep the investigation personal, and their respect is genuine on both sides, which is what makes the ending land.

Ishigami's stated principle is that a problem can be made unsolvable by arranging it so the solver asks the wrong question — the difference between a problem that is hard and one that has been misdescribed. That distinction is stated early and is the key to everything, in plain sight.

The woman being protected is a former hostess working in a lunch box shop with a teenage daughter and an abusive ex-husband. Her position is precarious and her gratitude is complicated by fear of the man protecting her, and the novel takes her situation seriously rather than using her as a prize.

The title names the book's actual subject. The scheme is an act of love by a man who has had no reciprocal relationship in his life, directed at a neighbour who barely knows him, and the extent of what he is prepared to do is the source of the final section's force.

It won Japan's Naoki Prize, sold in enormous numbers and made Higashino a mainstream literary figure rather than a genre one. It is the third in the Detective Galileo series but is entirely self-contained, and it is the usual entry point for readers in English.