Max and the Midknights (book 1) by Lincoln Pierce

Max wants to be a knight! Too bad that dream is about as likely as finding a friendly dragon. But when Max's uncle Budrick is kidnapped by the cruel King Gastley, Max has to act...and fast! Joined by a band of brave adventurers--the Midknights--Max sets out on a thrilling quest: to save Uncle Budrick and restore the realm of Byjovia to its former high spirits!