In the mid-80s Phillip wrote a book for Beth entitled Zanzibar. Set in the 1920s, the novel was a love story he wrote, partly, in an effort to win her back.
Coop learns that Blake submitted his book about Beth to a publisher. She has no idea that the book isn't about her.
Matt: (about Natalia) That is one nice girl.
Frank: Matt... don't even think about it.