In “Verity,” it’s hard to know who to trust. There’s Anne Hathaway’s titular character, a wildly popular novelist who is unable to speak or move after a car accident, but whose secret, and disturbing, autobiography speaks volumes. There’s Dakota Johnson’s struggling author, Lowen, who has been hired to finish Verity’s remaining novels and who finds herself living in Verity’s home and fantasizing about her more successful counterpart’s life, and husband. And then there’s a...