Fanning will play a teen girl who learns that a classmate who died in an accident had secretly wanted to be her friend, according to Deadline.
Written by Kevin Henkes, the novel won a Newbury Honour in 2004. A screenplay is currently being written by newcomer Christina Hammonds Reed.
The project was reportedly optioned by producer Donald Rosenfeld after Super 8 actress Fanning told him the novel was her favourite book.
Rosenfeld, who produced Dakota Fanning's movie Effie, said of the Fanning sisters: "I haven't worked with a more dedicated actor than Dakota, and can't wait to work with Elle. There is such talent. They are young, but they are old souls."
Elle Fanning is currently filming the upcoming Disney fantasy Maleficent, which stars Angelina Jolie in the title role.
Watch Elle Fanning talk to Digital Spy about Super 8 below: