As far as we know Adam and Mia are still together. The book ended with them getting back together and being all happy. There's supposed to be a movie to this but they haven't made it yet, i don't even know if they've started to plan it all out yet, but i hope they make it soon. The book was published on April 5, 2011.
Gayle Forman: was born June 5, 1970 and is an American young adult fiction author, best known for her novel If I Stay which topped the New York Times best sellers list of Young Adult Fiction and was made into a film of the same name. In 2007, she published her first young adult novel Sisters in Sanity which she based on an article she had written for Seventeen. In 2009, Forman released If I Stay, a book about a 17-year-old girl named Mia who has been involved in a tragic car accident. The novel follows Mia's experience as she lies in a coma fully aware of what is going on around her and everything her visitors say and do. Feeling the agony of the loss of those closest to her, yet aware of the abounding love of those that remain, she must make the choice to hang on or let go. Forman won the 2009 NAIBA Book of the Year Awards and was a 2010 Indie Choice Honor Award winner for If I Stay. The film adaptation of If I Stay, starring Chloë Grace Moretz, was released in the United States on August 22, 2014. The sequel to If I Stay, titled Where She Went, was released in 2011. Told from Adam's point of view, the novel is about Adam and Mia's relationship after the accident. In January 2015, Forman released I Was Here, about an 18-year-old girl dealing with the sudden suicide of her best friend. Movie rights to the book were picked up by New Line Cinema one month later. Forman is currently working on her first adult novel, titled Leave Me and due to be released in 2016. Forman won the British Fantasy Award (2010), and the ALA/YALSA Quick Pick for Reluctant Young Adult Readers (2010). She was nominated for the South Carolina Book Award for Young Adult Book Award (2011), the TAYSHAS High School Reading List (2010), the Goodreads Choice Award for Young Adult Fiction (2009), and the Milwaukee County Teen Book Award (2010). She has a husband and two daughters, one of them adopted.Here are a list of the books she's written,
"You Can't Get There from Here: A Year on the Fringes of a Shrinking World" (2005)
"Sisters in Sanity" (2007)