The Compleat Enchanter (1975) by L. Sprague de Camp and Fletcher Pratt is a collection of the first three Harold Shea books from the 1940s. The book is most notable for its inclusion in Appendix N of the first edition Dungeon Master's Guide as an inspiration to that game.
The stories center around Harold Shea, a modern man and psychologist who travels to different literary adventure universes. "The Roaring Trumpet" is Norse myth, "The Mathematics of Magic" is The Faerie Queen, and "The Castle of Iron" is Orlando Furioso (a tale that I've never heard of before). The stories themselves are tongue and cheek, as Harold is a modern man in a highly stylized and not-at-all politically correct tale. If you've ever wanted to see cultural appropriation in its native habitat, this is it.
The tales themselves read dully. I had to take rests to actually read this book through.
These are sexist tales. There no denying it. Oddly enough, Harold is bored of all the "approved" women stereotypes and wants one that's spirited. Here's an indication that the requirements on women of the day were so restrictive that even men were wanting to loosen things up.
When it comes to D&D, this book is rife with source material. Verbal, somatic, and material components for spells originate from these tales. In there, we also see scaled trolls with pointed noses, the basic giant types, web spells that are burned with flaming swords, flying carpets, illusions, fool's gold, magic choking hands, random encounters, and a great deal of the tongue-in-cheek humor that pervades early D&D.
While it's not badly written, I can't recommend the book. It's not a total stinker, but aside from curiosity or raging determination, there's no reason to go here. I'll happily lend you the book if you do. You don't need to give the book back.