The goldfish boy
(Book)

Emotionally crippled by his obsessive-compulsive disorder, teenager Matthew Corbin rarely leaves his room on a cul-de-sac in London, and he passes the day observing and writing down his neighbors doings from his window--but when a toddler staying next door disappears Matt is the key to solving a mystery and possibly saving a child's life...if he can manage to expose himself, and his secret guilt to the outside world.

750,Lexile.