John Green not only received the Innovators Award at the LA Times Book Festival, but also went on stage to talk about his book, nerdfighteria and the TFIOS Movie. He "gave his nod of approval to the film" and said, “The reason that it’s good is because Shailene Woodley and Ansel Elgort … they took the book very, very seriously and cared so much about the characters. In some ways I think they understand the characters in a way that I couldn’t.”
He also mentioned that the filmmakers also had another incentive altogether, that made them stay close to the book, “They were really scared of the readers of the story,” Green said. “They were genuinely afraid.”
Check out the rest of the article, in which he talks about internet communication and "The Catcher in the Rye" at the source.