Well, not an accurate answer, anyway…
More books to look for: Evangeline Walton’s Mabinogion tetrology, almost any of Charles de Lint’s books (but especially Moonheart, Svaha, and Jack the Giant-Killer), Andrew Lang’s Fairy books (oddly enough, they are much much more true to the original dark tales than one would expect considering when they were published), and Thomas Keightley’s The World Guide to Gnomes, Fairies, Elves, and Other Little People.
How about Rose’s Spirits, fairies, leprechauns, and Goblins? It’s been awhile since I’ve read it, but I recall that it had a quite a bit of info about various supernatural creatures (dwarves, fairies, and gnomes included) that was taken from folklore, not modern fiction.
Emma Bull’s “War for the Oaks” is an urban fantasy with creatures inspired more by traditional folk tales than most.
I second the DeLint recommendation. Almost anything by him is worthwhile.
Greg Bear, better known for hard SF, also wrote a few fantasies. “The Infinity Concerto” was reprinted as “Songs of Earth and Power” and featured an interesting take on the traditional Faerie world.
The Prydain Chronicles, a series by Lloyd Alexander is almost as good as the Narnia series by C.S. Lewis. Prydain elves and “little folk” are inspired by Welsh mythology while Narnia mixes traditions and creatures from several cultures, including Christian myth.
There’s also “Faerie Tale” by Raymond Feist that uses the older, nastier, traditional fairy stories as inspiration.