A monstrumologist is one who studies and hunts monsters. Dr. Pellionre Warthrop fits the description. His assistant is 12-year-old William James Henry, whose parents are dead and whose father died (horribly) while working with Dr. Warthrop, who plies his trade in New Jerusalem, a New England town not found on any map (but then true places, as we all know, never are).
Author Rick Yancey is given a series of bound volumes of handwritten memoirs written by Will Henry, the first three of which form The Monstrumologist and prove once again how much YA writing has changed since my own youth. Blood, entrails, maggots, violent deaths, dissections, madness, grave-robbings, and , of course monsters fill the pages. But then, what would you expect when New Jerusalem is beset by a bunch of anthropophagi? Yes, those creatures whose heads lie beneath their shoulders, as do their terrible shark-like teeth that allow them to rend the flesh of their only prey: us.
The book began fast, slowed down, and then careened to a finish. Things really picked up when John Kearns arrives. He's a monster hunter as horrible as the things he hunts and the most fascinating character in the book. It doesn't appear likely that he'll be in the sequel, more's the pity.
If you have a strong stomach and a liking for the outré, this might be just the thing you're looking for.