“The Devotion of Suspect X” is confined to a box. The edges and borders are established and then it works its way back over itself, revealing layers. This mystery stays within itself, an admirable trait. 
Every scene counts. You might think the opening is nothing but background scenery, a throwaway. You’d be wrong.
There are few principal characters (although the book hardly feels under-populated). There’s the teacher Ishigami, a “heavy-set man, with a big, round face that made his small eyes look thin as threads.” There’s Yasuko, who is dealing with an angry ex-husband. (Yes, she “deals” with him.) She’s Ishigami’s neighbor and, it turns out, Ishigami is fixated on her. The other two main characters are Yukawa and Kusanagi, who like playing chess together in Lab 13 at the Imperial University, in the physics department. Kusanagi is a cop. Yukawa is a college professor.
There’s one body.
We know who did it (by page 18).
At its core, “The Devotion of Suspect X” is a battle of wits. If you know mathematical theory, you might have an edge up on enjoying this plot, but I know precious little and still enjoyed it. The story is a match between detectives (those with official badges and those without) and the mastermind of the cover-up.
Very few books peel back the layers of the plot so carefully, so effectively. Very few books take you right down to the last page with plausible twist neatly connected to the next plausible twist. Emphasis on ‘plausible.’ You realize at the end that Keigo Higashino has adeptly kept a key part of the story from you—and you didn’t even notice.
I enjoyed the process of watching the detective and his professor friend break down the alibi, think through the logic of the situation bit by bit by bit. They prove, irrefutably, that a lot of police consists of “barking up the wrong tree.” Assumptions, theories, tests.
The approach to solving mathematics proofs comes in handy:
“Therefore, it would seem that analyzing the validity of someone else’s solution was simply a matter of following the routes they had taken. In fact, however, it was never that simple. Sometimes, you could follow a mistaken route to a false treasure, and prove that it was false could be even harder than finding the real answer.”
More: “All you’re doing is tracing the steps of the proof. What you should be doing is looking to see if there aren’t any other answers that might fit what you know about this case as well. Only if you can prove that are there are no legitimate answers other than the one he’s offered can you say that his is the only solution to the problem.”
Agatha Christie, who knew something about setting up the rules of a story (and sticking to them) would have been proud of this plot and the way it’s told.
Don't Need A Diagram 