Asher has a hard time fitting in at his new school, but he does manage to make a friend there, Rosie. Asher is a bit "feral" while Rosie appears to be a goody-goody (but we quickly learn that she's learning to be a wild girl herself - piercing her nose, smoking pot, etc.). They connect. And when Asher is unjustly accused of stealing, the two of them decide to run away.
The book has a quirky style of constantly-shifting viewpoints and writing styles. You'll either love it or hate it. Some passages are free association, others are dialogs (with none of the speakers identified), and there's some lists and poetry. The narrators shift between kids and adults. As a result, I spent the first 40 or so pages just getting oriented to the style.