Characters
- Christopher Boone, the main character of the story. Christopher is a 15 year old boy who has some behavioural issues, caused by him having autism. He enjoys mathematics, his pet rat Toby, and his studying for his upcoming A level math test. He dislikes the colours brown and yellow, and doesn't like being around strangers, as it makes him feeling uncomfortable. He sets out on a murder mystery to find out who killed Wellington, the Shears family's dog, against his father's orders. He is writing a book about his adventures, and receives help from Siobhan on how to write his story.
- Judy Boone, Christopher's mom, is a seemingly loving woman. She is more lenient towards Christopher, though she is less patient than Ed is. She lives in London, after moving away from her husband and Christopher. She works at an office in London in a temporary job.
- Ed Boone, Christopher's dad, is a somewhat stricter parent than his wife is towards Christopher, though he is more patient. He lives in Swindon serving as a single parent for Christopher for a few years after "his wife died of a heart attack." He works as an engineer. He dislikes the idea about Christopher investigating Wellington's death.
- Siobhan, Christopher's mentor, works with mentally challenged people like Christopher, and teaches him about the aspects of life, and how to behave in such a society.
- Eileen Shears, Christopher's neighbour, is the owner of Wellington. She tries to console Ed and Christopher after she hears about Mrs. Boone's passing.
- Roger Shears, Christopher's ex-neighbour, moved out of his wife's house to go live in London, with Mrs. Boone.
- Wellington, the Shears family's dog, was killed in the beginning of the story, and Christopher sets out on a journey to investigate and find out who killed him.