What books traditionally assigned in high school English/Lit courses are worth rereading as an adult?

Books like: To Kill a Mockingbird, Slaughterhouse Five, Animal Farm, any variety of Steinbeck that gets assigned.

I was not the most studious in high school and missed out on a lot of classics simply because I didn’t want to read an “assigned” book.

So what did I miss? What is a must read in adulthood?