Tess Gerritsen's Jane Rizzoli/Maura Isles series of crime thrillers are generally known for ending their plots within the same books, even though some subplots carry on throughout the series. That's what makes The Mephisto Club so interesting; this time, while the plot does conclude, there are a lot of unanswered questions that make me wonder whether Gerritsen has a plan to continue or has just decided to try for a semi-ambiguous ending. Either way, it's a treat to read, though it's not the strongest entry in the series.

It's Christmas, but murder never takes a holiday. Boston criminal pathologist Maura Isles and detective Jane Rizzoli are called away on Christmas Eve to a grisly house where a woman's dismembered body is found along with a Latin phrase, written in blood: I HAVE SINNED. A call was also made from the house to Dr. Joyce O'Donnell, a woman fascinated by murderers, studying them for her books. Following up on O'Donnell leads Rizzoli to an organization called the Mephisto Club, one that says it studies evil, says it's on the side of the angels, and appears to have friends in high places. When another corpse and phrase appears at their door, though, they start to consider that they may be the target instead. Is evil from the dawn of time reaching forward to finally take its rightful place in power?

The Mephisto Club is a lot more metaphysical than I'm used to from Gerritsen. While there has always been talk of "evil" in her books, it's been more about the evil potential of the human race than about historical belief in evil's existence. This book changes some of that, harkening back to biblical times and telling about apocryphal books of the Bible that describe demons walking the earth and such. The murders seem mostly mundane, but they're wrapped in this shroud of mysticism on which Gerritsen never fully claims one side or the other. It's clear that the members of the club believe in this ancient evil, as do the killer(s). That appears to be enough.

Once again, Gerritsen gets inside the heads of all her characters and makes them truly three-dimensional. For once, the interludes that don't involve Rizzoli or Isles are actually in the present day, as we see Lily on the run in Europe from someone who seems intent on hunting her down and eliminating her. Lily is a marvelous character, not afraid to do what's necessary to survive and running from city to city, hoping to find someplace that she can stay for more than a little while. As always with Gerritsen, you're never quite sure for a while what the two plotlines have to do with each other, but they inevitably dovetail nicely as the non-Boston gives us vital clues to what the murder plots are all about. I didn't regret the time spent getting to know Lily, and that's a compliment to Gerritsen's writing.

Of course, the strength of this series is the characterization of the regulars, with Rizzoli and Isles coming through with flying colors. Rizzoli has grown so much; she's still tough as nails, sarcastic to a fault and cynical, but she's a warm person who cares deeply behind that façade, and she grows even more in this book. Much of that has to do with her family. She begins to truly understand what's been going on with her parents all these years, and her newly developing relationship with her mother is a joy to read about.

Isles, unfortunately, isn't quite as strong, though she's certainly up there. The main problem is that she continues to think with her hormones a bit too much. I know there are people like that out there, so I'm not saying she's not realistic. But I'm getting tired of one of her first thoughts when she meets a man being how attractive and striking he is. Her relationship with Father Brody remains interesting because Gerritsen has spent a few books progressing it, but I just rolled my eyes when Isles met the head of the Mephisto Club and that thought immediately entered her head.

As to the plotting, Gerritsen continues the intricate murder plots that I have loved about this series. Once again, I found one of her books almost impossible to put down as The Mephisto Club kept me hooked no matter how much I thought about leaving it to do something else. Inevitably I would say "just one more chapter, and then I'll do" whatever it is I was thinking of doing. Gerritsen's prose style is just so absorbing, with the twists and turns of her plots keeping the reader captive. She knows just the combination of personal plot and murder plot to give the reader so that fans will be sated but those who don't really care about the personal won't be kept away from the murders for long.

The only minor fault, mentioned above, is the ambiguous style of the book. We never find out any deep dark secrets about the club, how they are so powerful that they can get involved in police investigations without anybody batting an eyelash (incidentally, these make some of the best scenes when they keep popping up in front of Rizzoli), or whether they are actually correct in their beliefs. The Mephisto Club can be taken at two levels. One is that the killer(s) is/are deranged and the Club is deluded but still doing a good thing. The other is that there are mystical forces out there which may explain many historical madmen, and we just have to deal with them as best we can. Gerritsen's afterword, where she explains where she came up with the idea for the book, actually muddies the water as she says she was coming from a position of (paraphrased) "what if these apocryphal books were actually history?" Whether or not she truly believes that, it's obvious she wanted the Rizzoli/Isles mythos to examine the question, and it unsettled me a bit that she leaves it up in the air.

But that's a stylistic choice that I certainly have no problem with her making. She does leave it so that those who don't want any mysticism in a "realistic" series can come down on one side and those who wouldn't mind it can come down on the other. Since I don't mind it either way, that's probably why the ambiguity bothers me. Whether it will bother other readers, I don't know.

The Mephisto Club is another must-read by Gerritsen if you have any interest in crime thrillers. While suffering in comparison to what I consider her masterwork (Vanish), it's an interesting book that will hold your attention to the end. Since I never know whether this will be somebody's first Gerritsen book review, I feel I must point out again that she has definitely toned down the gore, though it's still in there at times. If you have a weak stomach, prepare yourself and you should be fine. Otherwise, give it a try because I know you won't be disappointed.