Lovecraft’s three key recommendations for vital encyclopaedias of the classical world, given by him in Fritz Leiber and H.P. Lovecraft: Writers of the Dark (2004). All now online…
* Harper’s Dictionary of Classical Literature and Antiquities. Probably had by Lovecraft in the Second Edition, 1897. Owned by Lovecraft, but its whopping 1,700 pages explains why he was unwilling to mail it to Leiber as a loan. Lovecraft also called it… “a volume without which I could not exist”, suggesting another reason for not parting with it on loan. It is obviously an extremely comprehensive work, so much so that one has to wonder why Hypnos has only the most cursory four-word entry: “The god of sleep.”.
* Manual of Classical Literature : from the German of J.J. Eschenburg. Owned by Lovecraft in his grandfather’s 1846 edition.
* Baird’s The Classical Manual. Owned by Lovecraft. A sort of student equivalent of the above manual.