This book, like so many others, begins with the author proclaiming, "Everything you know about vampires is wrong!" and ends up leaving readers with the impression that nearly everything they knew about readers is, in fact, right. Jinks's vampires do sleep during the day, drink blood, create other vampires when they feed on humans, and can be killed by being staked. In most ways, traditional vampires. They've also chosen to (or been coerced into) following a non-human diet, complete with the support group of the title. Guinea pigs, here, with supplements to add nutritional value. The only real difference is that, instead of having fabulous supernatural powers, Jinks's vampires are weak and spend most of their lives physically ill. Of course, it does make being a vampire sound less than appealing, but it doesn't really make for a compelling and interesting cast of characters, seeing as that they spend most of their time in the bathroom.
The book is mostly concerned with setting up this totally unappealing lifestyle, but there is something bigger going on. First, one of their group (the most unsympathetic, of course) is staked by a wannabe slayer. Then, in the course of their investigations, they come across a werewolf fighting operation, where they rescue the captive werewolf. Both would have been more interesting if Nina were a bit less self-absorbed, which she describes as being a symptom of vampirism.
It's an interesting take on vampires, but I think that Jinks went a little too far in de-glamming them, ending up with characters I'd rather put to bed than read about.