Back when I was in high tech, my quickest route to sleep was to read something technical (algorithms, software design, data comms, encryption) that I didn't *quite* comprehend. (basically telling my brain "it's sleep or this"). I'd often be out in less than a chapter/section.

Bright side: in the morning, I would often understand whatever it was I'd been reading - and could explain it to other people (Feinman technique: you don't know something until you can explain it in a comprehensible way).

I'm still doing similar, but more focused on cellular biology and carbon chemistry.

I'd tried audiobooks, but my problem with them was that they were too engaging.