I've found audiobooks work really well - there's no screen glow to keep you up and most players let you set up a shutdown timer.

The Audible edition of Gibbon's "Decline and Fall of the Roman Empire" has worked really well for me: it's a fascinating panorama of history, but very episodic so you don't miss out on plot points if you actually fall asleep; the writing style is clear, elegant, and often funny; and the narrator has a calming voice and a smooth even tone throughout all 1300+ years of history so you won't be jarred awake by changes in volume.