If you have one great book or article in hand, what can you do to find more like it?
Follow citations backward and forward
References (older than the source at hand)
"Citing Sources" or "Cited by" (newer than the source at hand)
Click the links for "Related" or "Similar" sources (in Google Scholar and other databases)
Follow the author (in databases and/or on social media)
Plug the title into MathSciNet, get the primary MSC code, and see it that takes you.
Similarly, look at assigned "Subjects" or "Keywords"; use them to find more articles with that same subject.