EW has a chit chat with Jessica Chastain and a picture of her, giving the first real look at the film. Chastain plays Molly Bloom who runs a high stakes poker game. Chastain on the film:
Basically, the film follows along with the book, but also a lot of very interesting things happened to Molly after the book came out, which includes being arrested by the FBI, and so [Aaron Sorkin] really has woven together the different parts of her life: her athletic and academic excellence, alongside with going to Los Angeles and trying to figure out what one has to become to be a leader and to find success — and all that is also woven with her court case.
She talks about Sorkin, the part, the research and meeting the real Molly over at EW.