The Monstrumologist by Rick Yancey

Definition of monstrumology:

1: the study of life forms generally malevolent to humans and not recognized by science as actual organisms, specifically those considered products of myth and folklore.

2: the hunting of such creatures.
The Monstrumologist by Rick Yancey is the tale of Dr. Pellinore Warthrop and his assistant Will Henry. Will is an orphan under the care of Dr. Warthrop, a peculiar man who studies dangerous creatures and monsters. In the middle of the night in 1888, a nightmarish specimen is carted to the monstrumologist's home. Will can barely stand the sight of a half-eaten girl and an anthropuphagi, which is a vicious man-eating creature without a head. Will is forced to assist the intense doctor and is eventually led on a quest to find more of the creatures.
from Guys Lit Wire