L. Sprague de Camp sort of pioneered this, IMHO. The Reluctant King trilogy is probably the best, but also the Harold Shea Enchanters series. And his Krishna series (which is more planetary romance, which is basically fantasy without the magic).
None of which seems to be available in e-book form.
Actually, speaking of planetary romance, you might like Gordon Dickson's "The Right to Arm Bears", which is nothing like the title, but deals with somewhat comic adventures on a world full of talking bears