For Whom the Bell Tolls ! ! ! One of the best books, impossible to put down, edge of your seat kind of stuff, heartbreaking, etc. etc.! It's set in a war of course but I don't think I'd necessarily consider it a 'war novel' especially set against stuff that's basically memoirs.
You should reread Grapes of Wrath even if you read it in high school because it's so good and it's easy to miss artistry and beauty when you're forced to read something for a high school English class! If you don't mind something a bit longer I just finished East of Eden which is really incredible in breadth and somehow manages to be fairly concise (?) and consistently compelling, and is one of those novels that is so basically and classically American.
Homage to Catalonia by George Orwell is a really interesting companion to For Whom the Bell Tolls, Orwell actually fought in the Spanish Civil War and he fights from sort of the 'other side' of the Republican forces. Orwell's writing is also funny and clever and is really the picture of what journalism should be, making his biases (there's no such thing as writing without bias etc.) very clear. It also puts other Orwell which you may have read into a bit better context, plus it's neat to read an author who's so deeply associated with satirical/allegorical writing doing something so plain and straightforward.
If you want to read stuff that you can talk to people about, Haruki Murakami has been really popular for a while and his books are nice and clever and entertaining, not too dense, if a bit formulaic once you've read a bunch (he is - to use an unfortunate cultural pigeonhole - kind of a Miyazaki for lit). I think 'Kafka on the Shore' is a good starting place and the short story collection 'the Elephant Vanishes' is really fun, too.
I also think Kurt Vonnegut is great, super short reads (even if the page length starts to swell his writing is really straightforward) that I think are socially and culturally relevant still and like, come on, everyone loves some Vonnegut. So, if you've already read some but haven't read Mother Night or Breakfast of Champions those are definitely two of my favorites. I was initially turned off by Cat's Cradle which seemed like your standard obnoxious 'i'm a writer hard sciences are silly' kind of thing but he actually went to Stanford for chemistry and Carnegie Mellon for mechanical engineering and comes from a really important scientific family, and finding that out kind of lead to me reassessing and really liking that aspect of what he was saying as well (it's more nuanced than it may initially seem).
As far as Russian lit goes I would say don't just jump in and read Crime and Punishment and War and Peace because they're slogs (well, especially War and Peace). Dostoyevskiy and Tolstoy also have a tendency to create these really interesting complicated moral quandaries and then at the end be like 'lol nvm god's cool' which I imagine can be frustrating for a first time reader after 800-odd pages. Also just from an artistic standpoint Russian literature is very referential and it's a completely different cultural vocabulary as far as allusions to previous works go so you can miss a lot of interesting stuff as a foreign reader.
The real treasure trove for an American is the Russian short story/novella which every important Russian author wrote plenty of and they're really consumable and accessible. There's a saying that 'if you haven't read Gogol then you can't read Russian literature' which is really speaking to the fact that you should read short stories like Poor Liza (Karamzin), the Overcoat (Gogol), the Nose (Gogol), Bobok (Dostoyevskiy), Queen of Spades (Pushkin), etc. before launching into the 'great novels'. Doing a little bit of research into Orthodox Christianity probably also wouldn't really hurt for understanding some subtlety but I'm also a nerd for that sort of stuff so it's probably not important. Also if you decide you're going to read something and you can manage to find it, look for a translation by Richard Pevear and Larissa Volokhonsky, they're really good and translation makes all the difference for how much you're going to enjoy what you're reading. They also maintain the Russian system for addressing people which is important for understanding how characters are interacting in my opinion (I don't really like reading translations where this is simplified) but also kind of confusing, but they have explanations at the beginning of their books.
And have fun because reading a book you don't like is lame!
