Consider other works with "outsider" protagonists, such as Daniel Keyes' Flowers for Algernon, Judy Blume's Deenie, and J.D. Salinger's The Catcher in the Rye.
Consider other novels that use illustrations in innovative ways, such as Sherman Alexie's The Absolutely True Diary of a Part-Time Indian and Jennifer Egan's A Visit from the Goon Squad.
See also the Sherlock Holmes stories and novels by Sir Arthur Conan Doyle, especially The Hound of the Baskervilles, which is featured prominently in The Curious Incident of the Dog in the Night-time.