Madhouse  (English, Paperback, Thurman Rob)

Half-human Cal Leandros and his brother Niko aren't exactly prospering with their preternatural detective agency. Who could have guessed that business could dry up in New York City, where vampires, trolls, and other creepy crawlies are all over the place--if you know where to look. But now there's a new arrival in the Big Apple. A malevolent evil with ancient powers is picking off humans like sheep, dead-set on making history with an orgy of blood and murder. And for Cal and Niko, this is one paycheck they're going to have to earn. If they live long enough to collect it...