The answer to this question is found on the first page of the Chapter 1, which states, "It was in this town that I'd been compelled to spend a month every summer until I was fourteen" (3). When Bella turns 14, she says, "I put my foot down," (4). After that she spent two weeks in California with her dad.  But as the book opens, this year is different because Bella is going to stay with her dad for the school year.  Her mother is remarried, to Phil, and travelling with him, so Bella has agreed to leave Phoenix and live with her dad in a town she  hates.