Let’s get this out of the way first: it’s a fairies-in-America book, the first of the October Daye (Fairy PI) series. It involves the usual pointless feudalism and Native American erasure—the only non-Celtic creatures in the list at the front are djinn, lamia, and peri—but the racial politics are rather more crosslinked and nuanced than in most such.
The list at the front, unfortunately, set my expectations very low for the rest of the book; it’s a pronunciation guide, and it’s wrong. “Coblynau” (Welsh for “Goblins”) is plural, not singular, and it’s “cob-luh’nigh” not “cob-lee-now”; similarly, “Tylwyth Teg” (literally, “fair folk”) is “tuhl’with tair’g” (more or less) not “tillwith teeg”. As for “Tuatha de Danann”, that would have been even easier to research than the modern Welsh names are. As is traditional, they’re all presented as different species or clans, with distinct phenotypes; unusually, none of the traditional names are cultural analogues of one another.
Happily, I can report that the book improved. It’s a good, uncomplicated read, and the worse characteristics of fairies (imperiousness, secrecy, and drama queening, for instance) are presented as annoyances rather than good things. Toby herself is competent and proactive (rather too much so for her own good, at times) and McGuire’s both good at introducing interesting supporting characters and unafraid to kill them off when we’re getting fond of them.