I recently read The Forever War, which is considered one of the great early sci fi book by Joe Haldeman. Really interesting ideas and concepts.
This made me want to read some of the other classic sci fi books from that era like Solaris, Roadside Picnic, The Stars My Destination, the Dispossessed, the Left Hand of God, Stranger in a Strange Land, A Canticle for Leibowitz etc
Luckily these older novels tend to be relatively short.
On a side note I just finished Project Hail Mary - fun read, very much like The Martian, that I would recommend... They are adapting this into a movie with Ryan Gosling and... Emma Stone?!
https://twitter.com/user/status/1509969004781203457
I love Emma Stone, but no idea how she is going to play Rocky (for those who read the book, they know what I mean).
Hopefully, they'll pull off some magic, like how Arrival was completely different than The Story of Your Life, but still worked great... Just hope they don't somehow turn it into something its not, like a romance.