I'm very ambivalant about this series. One the one hand, the historical detail is amazing, and I truly enjoy the main characters. On the other, every book in this series seems to center around a sex crime of some sort, and it would be nice for a change of pace in that regard.
Add in a set of recurring villains who are either massively evil or insane, and the plot of The Pillow Book of Lady Wisteria is almost crushed by the sheer amount of moustache twirling.
That being said, I didn't hate the book. Sano and Reiko really make this series, and the political intrigue within the Shogunate is fascinating.
One thing Rowland does very, very well is paint a vivid picture of Japan in the 1600s. Currying favor and political maneuvering are a part of daily survival. I enjoyed watching the author's chess game unfold.
Sano and Reiko are likable characters, while still being very much a product of their environment.
While Reiko can defend herself admirably, she's far from Xena: Warrior Princess. In the glut of Urban Fantasy ass-kickers, it's nice to see a woman who can be awesome, while still staying true to the time and culture she lives in.
Likewise, while Sano is far from being a saint, he's deeply devoted to justice, and it's clear he loves and values his wife as an individual. In a time where women were considered little more than window-dressing, that's quite an accomplishment.
Thus, I'll be continuing this series. Perhaps the next book will contain a plot more worthy of the protagonists.