Writing a book about “all the [blank]?”

I’m a big fan of travel quests—a goal to visit a particular set of places, usually one that involves “visiting all the ________________.” So it catches my attention when someone writes a book that, well, could be a quest. Here are a bunch of ideas for anyone writing such a book. [24/31] for \#WeblogPoMo2024
[26/100] for \#100DaystoOffload