Decently well written, with an interesting concept.
Two major factors bothered me quite a bit, however.

First, the biology of the Anthropophagi, particularly when it came to reproduction, was both implausible and inconsistent.
We're asked to accept the premise that these primates have evolved to carry their young in cheek pouches rather than uteri (which they are lacking), and deposit them within corpses. Much like a wasp who lays her eggs within a dead grasshopper. So these pouches would be like eggs then, correct? They would have to contain nourishment for the developing embryo. But no, they appear to be nothing but a containment sack-- or else we're expected to believe that the young are fully developed before the tender age of two months, which is entirely implausible for a primate of that size. Humans do not even have functioning lungs at that stage, yet Anthropophagi are apparently developed enough to run and bite. Perfect, fully functional miniatures of the adults. I'd also like to know why a hairless creature that's native to Africa is so pale and pasty. And why we're expected to believe that it could evolve to be hairless and have distinctively larger eyes within the space of only one or two generations (24 years). All transparently unfeasible.
Also, at one point Yancey states that only a select few males are permitted to breed. Later, he contradicts this by saying that the Anthropophagi spend nearly all of their time either eating, sleeping or copulating.

My other issue is in the depiction of women. All live women (every single one) are either shrewish and nagging, corrupt, or outright monsters. All dead women (again, every single one) are pure, young, beautiful, and headless. And virginal. So virginal, in fact, that the one married woman who is found dead is the wife of a reverend, and found clutching an infant to her breast. Because she's not a virgin in fact, Yancey has to beat us over the head with comparisons to the virgin Mary.
This book would have been rather good (bad biology nonwithstanding-- if you're going to write a book, why not spend a fraction of a second doing actual research first?) if it weren't for this, Yancey's glaring misogyny. I would suggest skipping "The Monstrumologist", and picking up one of the many good Victorian horror stories of which this is such a pale imitation. Mary Shelley and Arthur Machen are great places to begin.