Character Developement

I'm about 1/2 way done with the book and I still can't put it down. Today while I was reading I realized the devolvement of Adam's character. At first, Adam's character was really vague. Mia mentioned Adam a few times as her boyfriend but not much more, until after the crash and Mia started looking over her past. At first, Adam was described as a rocker-boy, which is the complete opposite of Mia. Mia was a quiet girl, with few friends, loved classical music, and playing the cello. But as the story moved on Adam's character became more and more complex. He's in a rock band, but loves Mia's music, He's surrounding by tons of band-obsessed girls, but still chose Mia. This shows how much there is to learn about Adam's character the rest of the book.