There are so many options that giving a strong answer is impossible. I’m willing to recant everything in here.
“Should read” as in “should enjoy”: either Terry Pratchett or Victor Hugo, pretty much anything from either of them. I’d throw in also Dostoyevski and Le Guin. Pick a book from them and utterly enjoy every word, the world, the people that populate it, the driving concepts that structure the narrative.
“Should read” as in “important information”: Chomsky maybe? Yeah, let’s say Chomsky, in particular any chapter of Understanding Power. Or maybe Washington Bullets? Also extremely informative. Or Why we’re polarized. I’ll stop here, there are just too many options. All of these are historico-political books, mostly about how the US politcs has evolved over time, talking about internal media and propaganda, US interference into other countries, and the creation of the two party hatred system.
For “should read” = “should enjoy”, I would like to make a special mention of “Wuthering Heights” and “Villette” by the Brontes. I had a completely different experience from reading “Wuthering Heights” in my thirties vs when I read as a kid. The book’s atmosphere and the characters left a deep impression on me. Also, “Ivanhoe” by Sir Walter Scott. That book is such fun to read! Another one, “Demons” by Dostoevsky. A book that is interesting as well as slightly disturbing.
A dictionary
All of it? 😮