She announced the news at the New York Film Festival, reported Deadline.
Dunham, 28, said about the project, "This is actually my first time talking about it publicly. I'm very excited about it. I'm not sure when it'll happen, but I'm in the process of working on it."
She also expressed hopes of directing the film and detailed that she'd been interested in the book from a young age.
"I'm going to adapt it and hopefully direct it. It's hyper realistic and really pretty and it's full of incest and beatings, but it's a child's story. I've been obsessed with it since I was a kid," she said.