The Pillow Book of the Lady Wisteria by Laura Joh Rowland

The Pillow Book of the Lady Wisteria is the 7th book in the Sano Ichiro mystery series. Sano Ichiro is the Shogun's chief investigator, and the action takes place in 17th century Japan. Sano is bedeviled by palace intrigues and helped by his wife Reiko and his faithful lieutenant Hirata.

The mystery involves the murder of the Shogun's heir, Lord Mitsuyoshi, in a pleasure house in Yoshiwara--the quarter of the city where gambling, drinking, and prostitution are allowed. The woman who was with Lord Mitsuyoshi, Lady Wisteria, is missing, as is her pillow book.

Sano must solve the mystery in a hurry, because his political rivals are plotting to implicate Sano for the crime. Meanwhile, Hirata seeks to marry Midori--whose father is against the marriage. And, for some reason, Chamberlain Yanagisawa's wife is plotting to harm Reiko and the son she and Sano cherish.

There are now 11 books in the series. I've read several and have found them all involving and well-written. Read more about Laura Joh Rowland and her books here:

http://www.laurajohrowland.com/