The Salaryman's Wife - Sujata Massey
One of the best things about bookswapping is coming across series you've never heard of before.

In this case, it's the first book of a series set in Japan where our protagonist Rei Shimura (half-Japanese and American by birth) is teaching English and struggling to make ends meet by doing so. On a trip, she is the one who finds the dead body of a wealthy businessman's wife and initially one of the few who suspects that it might not be the suicide he seems to want everyone to think. Against her own better judgement, Rei gets involved with another visitor to Japan, this one a Scot who fits in very poorly.

What's interesting about The Salaryman's Wife is more the context of the book than the plot itself, which can't quite seem to decide whether it wants to be a serious crime novel or a slightly more fluffy romance. The series continues with Zen Attitude.