I want to read some french classics

So for context french is my first language but I almost exclusively read in english which I want to change. What are some classic french novels that I could start with, like the must-reads? I've read Le père Goriot by Balzac and liked it, but apart from that I haven't really read anything in french since highschool assignments. I'm still fluent so it can be complicated or outdated prose no problem. I don't have a type in particular, it can be dramas, tragedies, epics, mysteries, whatever as long as it's not too soapy and focused on romance.

Thanks in advance!