Roberts' character, Amy, is kicked out of her parents' home and is forced to take a job working at an adult film shop.
Critics seems to agree it's one of Cusack's best performances.
"Amy develops an artistic crush on Rat Billings (a hilariously droll John Cusack), a cranky, onetime poetry icon who perhaps too conveniently lives near Amy right there in Syracuse, N.Y.," Gary Goldstein with the Los Angeles Times writes.
"[Cusack] pours himself into every role, and even though the script to “Adult World” (by former TV writer Andy Cochran) relies on an overly familiar structure and some obvious gags, Rat transcends all that. He’s almost a consummate Cusack introvert and dreamer, a grown-up Lloyd Dobler gone just slightly sour. This is a performance of great subtlety, not a caustic caricature …," says Andrew O'Hehir of Salon.
Lou Lumenick with the New York Post said John Cusack is "still working at the top of his game."
"The tippling Cusack is darkly funny as he repeatedly, and snidely, disdains pleas to mentor Roberts," he wrote.
Check out the trailer below: