Can't agree on reading. It's cognitively stimulating, assuming you read something that interests you. I don't know about you, but I can't just close the book and forget about it.
Also try heavy books like Kant's Critique of Pure Reason. That one's another snoozefest for me.
Regarding Why We Sleep here is a critique [1]. Was posted on HN in past.
I think it just really depends, and it's worth just paying attention to how specific things affect you.
> but I can't just close the book and forget about it.
When I'm reading for sleep, It's closer to reading to the point of dropping the book rather than closing it and deciding to go to sleep fwiw!