Surviving Perilous Times: Lest Darkness Fall by L. Sprague De Camp — Alan Brown at Tor.com

“Lest Darkness Fall” is a 1939 drily comic science fiction novel by L. Sprague de Camp about a bookish 20th Century historian who’s suddenly transported to 6th Century Rome and sets out to prevent the fall of the empire.

Adding to my to-reread list.