Joe Dante would have been the ideal choice to direct a film version of John Bellairs’s 1973 young-adult gothic fantasy novel about an orphaned boy who goes to live with his warlock uncle in late-40s Michigan, but for some reason, the producers entrusted the project to misanthropic schlockmeister Eli Roth (Cabin Fever, Hostel). Perhaps they felt Roth was a good match for screenwriter Eric Kripke’s ruinous adaptation, which gives every character a schmaltzy backstory (thereby destroying Bellairs’s sense of mystery) and throws in lots of unnecessary bathroom humor. Jack Black (playing the uncle) and Cate Blanchett (as his best friend and partner in magic) are usually welcome screen presences, but they seem embarrassed and undirected here, and the less said about the child actors, the better. Still, the production design and special effects—which feel closer in spirit to Pee-Wee’s Playhouse than Bellairs—are enjoyable.