In the movie, Maddy's mother says Olly needs a haircut. In the book, Olly has a shaved head.
Olly's life at home was a bigger role in the book than in the movie. The book goes more into depth on Olly's life and his person.
There is a scene in the movie where the astronaut is sitting on a bar stool in a diner that Maddy created. This scene is a reference to the famous 1942 painting "Nighthawks" by American artist Edward Hopper.
In the movie, Olly has brown colored eyes. In the book, Olly is written to have ocean blue colored eyes and an olive complexion.