L Sprague de Camp and his wife Catherine were guests at a Pseudo/PsurrealCon (I forget which) in Norman, OK, about 20 years ago. By the way, the "L" stands for Lyon, his first name.
They were very nice, elderly people, very goodnatured about being surrounded by SF nuts, and possibly thankful that they were remembered at all!
Besides SF & fantasy, de Camp wrote nonfiction, such as his bio of good ol' Eich-Pee-Ell. Also a LOT of historical speculation and research, as in
de Camp wrote another noteworthy book solely on Atlantis, Lost Continents: The Atlantis Theme. It's also a fine read.
Be advised, de Camp is dry-witted, urbane, and restrained. He doesn't ramble on in florid prose with wild speculations.
But he's a fine researcher, and (given the time of the writing) the books are in-depth and insightful.