For instance, I'd like to read a biography on Churchill. Google will have you believe there are no more than about 10, whereas I'm sure the actual total is closer to 100 (correct me if I'm wrong). The same ones keep cropping up. No doubt they are the "best" but sheer comprehensiveness can obviously be an issue. 1000 pages is no jaunt. I recently chanced upon Sebastian Haffner's interesting looking <200 page bio purely because he's the author of one of the great works on Hitler. But what if he didn't write The Meaning of Hitler? Would I have found it?
Thx.
I know that larger university libraries are organized not by Dewey Decimal but the Library of Congress. It's really nice because it does organize things by category instead of author. Thus, if you go there and see a book about Churchill in the catalogue, go to the shelf and you'll find every book about Churchill that the library has. You wouldn't have to use Library of Congress system library, per se, but you could find one, get a list of books from there, and then start your adventure. Also, even if you're in a Dewey Decimal library, ask your librarian! That's totally their job: to find you as many sources as possible and they're usually quite good at it.
Otherwise, I don't think there's a definitive "nexus" that lists every book ever written. That'd be bananas.