The question you want to ask is if you hit your point and stayed on task, that's what determines your overall grade. The rest, such as details unrealated to main idea, spelling and grammatical errors, and text supporting words are minor peices that barely count to anything. As long as your text is clear and gets a point across, the rest will fall into place.
Its main character, and the narrator of the book, is Christopher Boone, a 15 year old with autism. Mark Haddon, the author of The Curious Incident, never lets Christopher stray from his unique interpretation of the world around him, which is what allows the readers to feel they are within his mind.