Inspector Imanishi Investigates is a 1961 mystery novel by Seicho Matsumoto. It's a Japanese police procedural. The story is told from the point of view of the main investigator, and you are privy to his thought process as he teases out the clues and follows leads. I enjoyed going on this journey and found the book -characters and plot and setting- interesting.
It was adapted for film in 1974 as Castle of Sand.
from the back of the book:
Inspector Imanishi ... Haiku poet, gardener, and the most dogged homicide detective on the Tokyo police force.The Practical Theorist says, "It’s so intensely atmospheric you really don’t want the book to end." The LA Times says, "In addition to being a good whodunit, "Inspector" offers a vivid portrait of the confused Japanese culture of the early '60s". AustCrimeFiction calls it "incredibly engaging".