This is one of the Powers books I haven't read, and since he's now written a sequel I figured I better start, so I downloaded it to the Kindle.
It's the usual Powers story that takes the historical details of the late years of Percy Shelley (including his encounters with Lord Byron, Mary Shelley, and John Polidori) and weaves a vampire story into the gaps.
It wasn't one of my favorite Powers books, but the well-crafted writing comes through, and I enjoyed that. It's just such a weird premise because these are not normal vampires but instead some different species, so none of the normal rules apply. In fact if they weren't named as vampires at all but instead just supernatural creatures that have a dangerous tendency to bond with unsuspecting humans. With that caveat it gets more interesting - and more like a personalized version of the genii in Declare, which I'm rereading right now.