What classic literature should we be sure not to miss?

I just found out my boyfriend isn’t familiar with Don Quixote. That’s strange to me because I consider it completely classic—I think my Spanish teacher read us a kiddo version in like first or second grade. It’s come up a few times in my schooling since then and in references in real life or movies.

It kind of makes me wonder what I’m missing in the same way. So… what classic might I be missing? And why is it awesome? Am I missing it in part because it is classic non-English literature?