While poking around for research material on ghouls, I found this online edition of Muhawi and Kanaana’s Speak Bird, Speak Again: Palestinian Arab Folktales. It’s got quite a number of tales about ghouls as they appear in Arab folklore, paralleling stories in older works such as the Arabian Nights.
In terms of the book, it’s difficult to figure out what exactly to do with these tales. Lovecraft and subsequent authors took ghouls in quite different directions from the shapechanging, fire-creating, house-owning, one-blow-kills-me-two-blows-revive-me model in the folklore. Perhaps I can make it a pleasant side bar or something of the sort.