A party of adventurers is creeping through an ancient archive, or rifling through the tools of a deceased Magus, or nosing through the private literary collection of a prestigious noble. They open a book. What do they find?
1) Browse to Wikipedia.
2) Click "Random Article" near the top of the left sidebar. (Optional: stay on the main page and glance at "Today's Featured Article" instead.)
3) Ask yourself if a book could be about the subject of this article in your game's setting. (Proper nouns may be interchanged freely. For example, the article on Adolf Hitler could, in your setting, be about some mythologically wicked villain from the sordid past.) If it could, then that is the subject of the book your players find! If not:
4) Click the first link in the article's body not in parenthesis.
5) Jump to step 3.
Far broader and deeper than a d100 table, and nearly as easy to use.
(Nota bene: this method DOES generate a fair proportion of towns and municipalities. This is not necessarily a bad thing. Substitute in a nearby town or other location in your setting, note some juicy assets and dangers in that location which the book mentions, and you have yourself an adventure hook!)