The entire book is written from an ableist and "inspirational" point of view. It was written by an able-bodied / biotypical person, who one day had a brief interaction with a child with facial differences. (Her son got upset upon seeing this other child.) It was out of this brief interaction that she became inspired to write a book of what she assumed that child's life was like, having no knowledge on the subject (nor even a conversation with the child she had encountered who had facial differences.)
She did choose to include a number of disabled slurs which she said she included with "careful deliberation".
There is no car crash. The main character was born with facial deformities from a rare gene disorder that is inherited from both of his parents. One boy makes fun of him in class and says, were you in a car accident?" but Augie says no.