Reading the most recent Anita Blake novel has made me ponder vampire series. Nothing is more prevalent in horror literature with a few notable exceptions (King's Salem's Lot, Brite's Lost Souls, and Brust's Agyar being the most notable ones), almost every vampire novel has spawned sequels. And, perhaps in keeping with traditional vampire mythology, the sequels, like the vampiric progeny, tend to get progressively weaker, until we're left with the literary equivalent of George Hamilton in Love at First Bite.
But there are a few vampire series that, even if they peak at the first book, provide enough entertainment throughout the series to be worthwhile. These series only have two things in common they have vampires as major characters, and they all contain five books or fewer. The second wasn't a rule I had when choosing the series, but it turns out that, as with almost any other series, familiarity breeds contempt, and even much more talented authors than Laurell K. Hamilton and Anne Rice (and all the authors I list are much more talented than those two) would have had trouble keeping series fresh beyond that number.