I was pretty disappointed when I finally read the book after seeing the movie. They're fundamentally different in tone. The movie made it this big, shiny, romantic space adventure, but the book 'The Passengers' is... well, it's colder, grimmer. Jim doesn't just wake up Aurora by accident after a year of loneliness. He actively obsesses over her for months, studying her profile and video logs, knowing full well what he's doing is morally monstrous. The book spends way more time in his head with that gnawing guilt. It's less a love story and more a psychological portrait of isolation and a really messed-up choice.
And the ending! Don't get me started. The movie gives them this magical fix with the medical pod and a happily-ever-after homesteading on a new planet. The book ends with them just... surviving on the ship, forever, with this massive lie between them. Aurora chooses to stay with him, but it's a bitter, complicated choice, not a triumphant one. The movie felt like it needed to sell tickets; the book felt like it was asking uncomfortable questions it wasn't willing to neatly answer.
I actually prefer the book's bleaker honesty, even if it's a harder read emotionally. The movie's ending always felt like a cop-out to me.