In the book, Hazel notices Gus when she finds a seat at support group. In the film, she chooses to take the stairs and collides into Gus on the way.
In the book, Gus invites Hazel over to see V for Vendetta. In the film, there is no mention of what film he wants to see with her.
In the book, Gus and Issac are fans of a band called Hectic Glow, which Gus introduces Hazel to. In the movie they don't mention the band except for a poster on Hazel's wall.
In the book, Hazel and her parents pick up Gus and drive to the airport. In the film, Gus arrives in a limo, saying that he told the Genies that he wanted to travel in style.
In the book, Hazel goes to visit Isaac after his surgery. They joke about the nurse after she leaves and he mentions that Gus visited and talked about her, before slipping into unconsciousness. In the film, the surgery has already taken place and Hazel and Gus inquire about Isaac's eyes before plotting to egg Monica's Firebird.
In the book, Gus announces to Monica's mother that a blind man is egging her daughter's car because she has wronged Isaac. In the film, Gus says that Monica has done a great injustice and that between the number of legs, lungs, eyes, and 2 dozen eggs they have, it would be best if Monica's mom got back inside.
In the book, Hazel's mom celebrates a variety of obscure holidays like Bastille Day and Hazel's Half-Birthday. In the film, there is no mention of her celebrating any additional holidays.
In the book, Gus calls Hazel when she is recovering from the lung scare and asks her to draw the diagram of virgins and smaller circle with him in the virgins circle. In the film, he picks up a stick and draws the diagram into the dirt on the way to the picnic near Funky Bones.
In the book, Hazel interacts with her friend Kaitlyn from time to time and considers her a good friend who is sophisticated and knowledgeable about boys. She consults Katelyn for advice about Gus early on in the book. In the film, Katelyn is not mentioned and does not appear – instead, viewers are left to believe that Hazel's parents are her only friends.
In the book, Hazel plays blind-man video games with Isaac at his house on two occasions. The first time, she meets his younger brother Graham, who tries to mess with Isaac's video game figure by having him commit suicide in the middle of a mission. The second time, both mock the system's limitations with understanding their commands like "Hump the cave wall" and "I dislike living in a world without Augustus Waters." In the film, Hazel and Isaac never play video games with each other.
In the book, Lidewij sent the notes Gus wrote for Hazel's eulogy. In the film, van Houten gave it to Hazel.
In the book, Gus mentions his not half-sisters, who are twenty-eight. In the film, they are not mentioned.
In the book, Hazel refers to herself as a grenade when speaking to her parents, but never mentions it to Gus. In the film, she only speaks about it with Gus.