Just finished 47th Samauri by Stephen Hunter. Atypically for an author who usually writes about firearms, this is about swords. The protagonist's father fought on Iwo Jima and took a sword from a Japanese officer who committed seppuku with it. Now 60? years later, his kid asks for it back. He doesn't have it, but finds out who does, agrees that returning it is the right thing to do, and brings it back to Japan and the guy's family. Then things get very violent because some bad guys discover the sword's very famous past. So naturally, Bob Lee Swagger has to quickly learn swordfighting and basically re-enact the 47 Ronin event to avenge his new friend's honor.
It's not the author's best work (for that I still recommend Black Light), but is interesting enough. The books in this series are self-contained, but do have an order. I had already read the book that immediately follows this one and knew how Bob Lee won the climactic swordfight, and what he brings home from Japan.