Sweeney was raised in Massachusetts and attended Harvard University and the University of Virginia’s MFA Program, where she was a Henry Hoyns Fellow.
Her first novel, Among Other Things, I’ve Taken Up Smoking, is about a girl who grows up alone with her father on an island in Maine and is sent to stay in New York City with friends of her father's who open up her past, and her own world, in ways she cannot begin to imagine. It was published by Penguin Press in 2007 and was an Editor’s Choice at the New York Times Book Review and the recipient of a 2007 Lambda Literary Award.