Start here with science fiction
People ask for the best science fiction novel as if there were a till receipt for that. There is not. There is a first one that does not feel like homework.
If you want people, start with The Left Hand of Darkness. If you want a problem to solve, The Martian or Project Hail Mary. If you want to laugh on a spaceship, Hitchhiker. If you want the future to feel like a city at 3am, Neuromancer.
After that, the shop is yours. The point of a first book is a second book.