What is the author's style in The Truth About Forever by Sarah Dessen?

The language used by the author of The Truth About Forever is casual and easy to read, but also articulate. It is appropriate for a book being narrated by a teenage girl who is known to be very intelligent and a good student. The language changes as needed to reflect various characters as they speak and write. For example, Jason's dialogue and e-mails are stiff, formal and somewhat stilted, reflecting his serious, brainy personality. By contrast, Monica's nickname of Monotone is reflected in her slow, slurred speech patterns, and Macy's mother's tense, high-strung personality comes through clearly in her dialogue.