The End of Everything
The End of Everything by Katie Mack.
Quantum nihlism
This was pretty interesting! I'd heard of a few of these theories from random Reddit posts, but the book obviously goes into much more depth and provides some science to back the theories up. I've soured on pop-sci a bit since in hindsight most of the stuff I've read is either pushing the author's political agenda or just has a lot of stuff made up to be more interesting, but this neatly sidesteps the issue by being about stuff which won't happen for billions upon billions of years....