Genetic modification goes horribly awry and fuckery ensues. There's eventually a prequel book about this that's pretty good so long as you remember that the main dude for that book and one of the characters in the regular series have damn near the same name. Mums and I were so damn confused because like, not human so it could've been the same guy, but wasn't acting right.

The only real downside to the series (and I can only go so far as to speak til the first time it ended) is that every time I read one, I desperately want a very, very saucy pizza. My dislike of tomatoes (as is) though feels very justified each time I think about the Hollows. :D