Shinju, by Laura Joh Rowland. It’s the first of a series, so if you like it, there are lots more to read. It's worth noting that early books in this series, including Shinju, are only available as eBooks.
The novels are murder mysteries set in feudal Japan when the samurai are the noble class, and the first one starts us off in 1689. This world is governed by Bushido, the ancient warrior code of conduct, which is known for being very harsh. It might seem hard to imagine a character you could relate to from this severe culture, but the author manages to pull it off with the honorable samurai Sano Ichiro.
Sano is a great sword fighter, an educated scholar, and an honest man who guards the rights of the unfortunate. And he’s good-looking too. He’s got it all, but there’s a catch – these traits don’t get you very far in his world (except the sword-fighting). Sano may be very likable and reasonable (to the reader), but his integrity tends to get him into trouble. Obedience to one’s superiors is critical in Bushido, and very often Sano’s personal code of honor, the pursuit of truth and justice, is at odds with his superiors’ orders. Shinju begins with an apparent double suicide that Sano is ordered to investigate as a police commander. Anyone else in his position would probably close the case right away, but something about it doesn't sit right with him, and he must find out the truth, even at great cost to himself.
I’ve learned a lot about Japanese culture and history reading this series, and it doesn't seem strange or distant. The main character is a samurai born and bred into Bushido, but still enough like us that I felt like I could understand him. This is a great series that will draw you into a whole different world.