Llewellyn, a letterpress artist in Tacoma, Wash., inks this first adventure with a mysterious house as its fulcrum. Narrator Josh and younger brother Aaron move into long-vacant Tilton House. Its tilting floors and walls covered in cryptic equations and diagrams captivate Dad (a museum employee) and unnerve Mom (a harried school office-worker). The boys, with Hermione-esque neighbor girl Lola, uncover layers of mystery involving a rat-infested attic and a crawlspace that might include a body, buried treasure or both. The appeal here is also the source of a cavil: The author includes so much kid bait that the narrative’s nearly trumped. There are creepy neighbors, a wooden-legged grandpa, invisibility, a dog, a mysterious box containing “grow powder,” stinky rat poop and much more. Additional, more authorial elements tackle family finances, yellow journalism and the fickle art world. A thread including a pair of undertakers whose long list of names portends death seems tacked on. Yet the author also nails the sibling cadences and camaraderie, delivering a genre-blending page-turner with plenty of room in its eaves for sequels. One to watch. (Fantasy/mystery. 8-11)