What is the main conflict in The Guernsey Literary and Potato Peel Pie Society by Mary Ann Shaffer?

While on tour through England to promote her book, Juliet receives a letter from Dawsey Adams, a member of the Guernsey Literary and Potato Peel Pie Society, and they begin to correspond. When she is asked to write an article for the "Times", she decides to include the Society in her article and thus begins writing to several other members, such as Amelia Maugery and Isola Pribby. Meanwhile, she begins dating Mark Reynolds, an American publisher. As Juliet develops close friendships with her Guernsey correspondents, she begins to wonder whether she can write a book about the Occupation, and she decides to visit Guernsey, despite Mark's protestations that she stay in London and marry him.