This Laundry book deals with quant-trading vampires. Their genesis is an unfortunate side-effect of mathematical research. In terms of supernatural baddies, these are some that I have rather more sympathy for than usual - they do computerised prop trading at an unnamed large British bank that didn't become government-owned. In other words, they're the people I used to sit opposite, although I'mm pretty sure that in the real world they're not vampires.
The Laundry series has collected quite a few entries by this point, and was in danger of becoming somewhat uniform. However, this book throws in a few curve balls, with a plot more complex than I was expecting, and an ending that fixes the immediate crisis but leaves many loose ends. The series was starting to weaken as the initial novelty of the Cthulhu/James Bond/Sysadmin cross-over wore off, but this book reinvigorates the series, making it one of the more enjoyable Stross books I've read in a while.