Relative newcomer Amber Heard will join Johnny Depp in his long-in-the-making adaptation of Hunter S. Thompson's novel The Rum Diary. Heard, who recently played Seth Rogan's girlfriend in Pineapple Express, will star opposite Depp in a love triangle set in Puerto Rico. Scarlett Johansson and Keira Knightley had been tied to the project, but withdrew after concerns about (ahem) excessive nudity. Depp starred in Thompson's Fear and Loathing in Las Vegas ten years ago, and was good friends with the author before he died. Although Diary has been in the works since 2003, Depp only signed on last year to play Paul Kemp, the film's alcoholic protagonist. Thompson spent 30 years writing the book, and it is said to be loosely based on his life.