Lest Darkness Fall (Sphere science fiction)

Lest Darkness Fall is an alternate history science fiction novel written in 1939 by American author L. Sprague de Camp. The book is often considered one of the best examples of the alternate history genre; it is certainly one of the earliest and most influential. Prominent alternate history author Harry Turtledove has said it sparked his interest in the genre as well as his desire to study Byzantine history.Lest Darkness Fall is similar in concept to Mark Twain's A Connecticut Yankee in King Arthur's Court.