Came to say The Selfish Gene for nonfiction. Changed the way I thought about things.
Reading the Selfish Gene today as an adult, when you've probably read a dozen similar books already, is not going to have the same effect. It's going to be pretty boring. That's why asking for book recommendations is flawed to begin with.
People are generally enthralled by Sapiens which is just a very mediocre extension + shallow interpretation of Dawkins’ thesis.
The importance of The Selfish Gene is to write a correct summary of the neo-Darwinian project. In the future (perhaps even now), it will be more famous for the coining of meme (in an appendix IIRC).
However, The Extended Phenotype is a remarkably original exposition of important (then) contemporary frontiers of Darwinism. It is a powerful idea, powerfully described.
It is certainly his most important original contribution to the literature. And a beautiful book. True and convincing. It will change your view of the world. There is no higher praise.
Also,
Bill Bryson’s “Short History of Nearly Everything”.
Brian Greene’s “The Fabric of the Cosmos” (and all of his other books)
Richard Dawkins’ “The Ancestor’s Tale” and “The Blind Watchmaker” are also amazing.
Fiction:
Adrian Czajkowski‘s “Children of Time” and Orson Scott Card‘s “Ender’s Game” are both anong my favourites.