Now on Archive.org in open PDF, the pre-PC A Dictionary of Fairies. It has a hideous American cover and a different title as An Encyclopedia of Fairies, but it is the same as the British A Dictionary of Fairies — which in paperback had this excellent 1979 cover from Tony Meeuwissen, immediately serving to reassure uncertain readers that the book is not about the Tinkerbell type of fairy.

The book is still highly regarded, and commands high prices even in tatty paperback form. Incidentally Lovecraft also wrote on fairies, on which see his “Some Backgrounds of Fairyland”.