In Freak the Mighty by Rodman Philbrick, are the main characters trying to achieve something or overcome a particular problem?

The main character of Rodman Philbrick's Freak the Mighty is Maxwell Kane, the son of Kenneth "Killer" Kane, who was convicted for murdering Maxwell's mother via strangulation. Maxwell's struggle throughout the book is to overcome his low self-esteem (he frequently refers to himself as a "butthead") and his reputation as a frightening presence in the community due to his resemblance to his father. 
Maxwell finds a friend in the form of another major character, Kevin, the titular "freak." Kevin's struggle throughout the book is to cope with the birth defect (Morquio syndrome) which has left him dramatically smaller than other children his age and which requires him to use leg braces and crutches to walk. 
Together, Max and Freak go on many adventures, including evading bullies, visiting the "Bionics Department" of a hospital, returning the lost purse of the wife of a motorcycle gang leader, and turning over Max's murderous father to the police after he is released from prison on parole.