Parasite Positive (Britain)
Peeps is a young adult science fiction novel; it is also a teen-aged vampire novel, and a bit of a science documentary type nerd-fest (of the good kind) as well. It comes across as a mainstreamed combination of Twilight and The Host, but as it was written three years before Stephanie Meyer started writing, Peeps is clearly a savant of the teenage-vampire genre.
This is the story of Cal; a freshman college student who made the mistake of sleeping with a vampire. He was lucky -- he didn't turn into a vampire/ghoul, but instead found himself as a mostly-human carrier of vampirism. This is a pretty good deal, overall. He is faster and stronger, can see in the dark and has super hearing. He craves protein and eats constantly, but he doesn't have the urge to eat people. This is a one-in-a-hundred chance, and automatically inducts him as a member of the Night Watch, an organization that captures the less fortunate, fully infected vampires and treats them -- or destroys them, if necessary.
These vampires are not traditional blood-sucking, cape-wearing Draculas. In many ways, they are closer to ghouls or zombies. They are scared of light, and live in dark spaces surrounded by broods of rats; they feed on other humans, but eat them whole. They are insane, having lost all higher cognitive function, but they make up for this by having heightened senses and being super fast and super strong.
What sets Peeps apart is the science behind the monsters -- they are infected by a parasite (peeps is short for 'parasite-positives'); and while the peep parasite isn't described in any great detail, other parasites are. Westerfeld gives us background on toxoplasmosis, Guinea worm, trematodes, malaria, lancet flukes, screwworms, and others. And he throws in lessons on epidemiology and ecology while he's at it, and mentions fun things like rat kings and various bits of mythology. The factual background is enough to convince the reader that the vampire parasite is a viable plot device, and that the world is a pretty cool place even if vampires are imaginary.
You may have noticed that I haven't said much about the plot. I could; Cal is put in charge of hunting down and containing everyone he had accidently infected, and then the woman who had infected him. While completing this task, he meets a nice uninfected girl and a few thousand evil rats. It quickly becomes apparent that the nice girl and the rats are all part of a greater mystery, an evil that makes cannibalistic ghouls look like small fry... In other words, just about exactly what you would expect.
This is a pretty good book, but it has some drawbacks. The main character is kind of immature, compounded by the fact that the parasite makes carriers very horny (to help them spread); making a horny college freshman the main character somewhat limits the number of people who will identify with him. Peeps also takes a bit to get out of cheesy horror-movie mode, and throughout the book the Night Watch continues to have a slightly cheesy flavor. And the main love interest uses the word 'dude' much to often. But these downsides are worth ignoring if you like teenage vampire novels, if you like geeking out over science when reading SF, or if you like Scott Westerfeld.
If you are scouting this book to decide if it is appropriate reading for your kid (or yourself), you may have already gathered that it is not as young-adulty as most books in the young adult section. It is generally recommended for ages 14 and up (grades 9-12), and doesn't have any graphic sex scenes -- but Cal does think about sex a lot and not in a particularly romantic fashion. It's not anything worse than the average TV sitcom, but at the same time I wouldn't recommend it to someone else for their children unless I knew where they stood on such matters. At the same time, it is probably a bit light for most older readers, making it rather limited in readership. Which is a pity, because it's a fun read.
There is a sequel to Peeps, The Last Days.