But is "French Revolution" the subject librarians use?
This link opens in a new windowLibrary Science, as a field, is about the organization of information so it can be preserved, rediscovered & reused, and ultimately expanded. We don't use obvious subject tags like "French Revolution" because there have been a lot of French Revolutions (ex. 1848). We also avoid common subject names because "obvious" terms change over time.
Part of your challenge while searching is to identify important keywords while also paying attention to librarians' subject headings. It can be tricky to figure out the official library subject, but once you do, you can find almost every book on your topic!