The Man Who Died (2017) by Antti Tuomainen
Good Reads meta-data is rated 3.82 by 4,917 litizens
Genre: krimi.
DNA: Finland
Verdict: TMI.
Tagline: DOA.
He went to the doctor with a headache and the doctor diagnosed something far worse. (See my review of the Brazilian short Instant Doctor elsewhere on the blog.) Hero finds that he has been irreparably poisoned and there is so much internal organ damage he has but weeks, perhaps days, to live. He sets out to find out who has killed him.
He suspects his unfaithful wife or her toy boy and …. Then his business rivals look like prospects. A satisfying array of red herrings are tested before he gets to the least likely candidate. Bingo!
This is a trope used before. The most vivid example I can recall at the moment is the film Dead on Arrival (1949).