I normally go out of my way to avoid vampire series novels, which Jon F. Merz's THE KENSEI is, but its premise was simply too wild to resist: a ninja vampire hunting organ traffickers in Japan!
Said vamp is Lawson, the headliner of several previous novels by Merz (none of which I've read). In THE KENSEI Lawson shows himself to be an irrepressibly cynical, world-weary martial arts enthusiast with a wise-crack for every occasion. He dispatches bad guys a’ plenty, stumbles upon a conspiracy to create vampire-human hybrids, and falls in love with a babe assassin named Talya. The book is well paced and mayhem packed, with robust, no-nonsense prose that pulls the reader along.
The author is an actual back belt ninja, having passed the Godan ninja test which Lawson takes twice in these pages. As delineated here (and seen on YouTube, which contains video footage of Jon Merz's February '03 Godan test), the test consists simply of dodging a sword swung at one's back by a grandmaster ninja. See also the acknowledgments page, in which Merz signs off with the words "To Dr. Masaaki Hatusmi...my sincerest and humble thanks for nearly cleaving me in two on that drizzly cold day in February 2003."
Other interesting real life tidbits imparted herein include some illuminating (and alarming) info on Yakuza infiltration of the entertainment industry in Japan, the formidable Japanese nightclub scene (which comparing with U.S. clubs is apparently "like comparing a kid's party at McDonald's to Disney World") and a vivid description of eating the fearsome blowfish, or Fengu--a dish that if cooked improperly emits a neurotoxin that causes a fast and painful death ("I took a piece of the meat and chewed it. The vague taste of chicken was replaced by a slight tingling of my lips...").
In short, THE KENSEI is fast, fun and informative. It won't change the world and nor does it intend to, registering as an entertaining action-oriented read, pure and simple.