Harold Shea stories by L. Sprague de Camp and Fletcher Pratt--tales of a 20th century American who gets transported to worlds of Norse mythology, the Faerie Queen, and other literary/mythological settings, on clearance for one dollar. As a bonus, this compilation includes a short forward by David Drake, another author I enjoy.
Anyone who plays Dungeons & Dragons could mine a treasury of adventure material from this series. Giants, dragons, knights, wizards, there in the mythological or literary roots of their settings.
It's easy to see why these works were listed as inspirational reading in the first edition Dungeon Master's Guide--mentions of cockatrice and griffons, dragons that smell of chlorine or spit poison, even a modern day-professor describing magic spells as having verbal and somatic components!
I'm about halfway through the volume, and it's a great read. Y'all should track this down and read it if you get the chance.