Though the experience seems new for every generation, teenagers have always faced hormonal chaos, romantic obsession, parental tyranny, peer pressure, crises of identity, and demons from another dimension. “Harry Potter,” “Twilight,” “The Hunger Games,” and others have dramatized this critical period to great success both in print and onscreen. For studios seeking another such franchise gold mine, Cassandra Clare’s “Mortal Instruments,” a hefty, best-selling sextet of YA novels, would seem the next big thing. Not only does it exploit the same demographic as those other properties, it shares swaths of their DNA. “All the stories are true,” goes a refrain in Clare’s book that is repeated in the film, and apparently they are also fair game for pillaging.
The trouble comes when these stories all take place at the same time. To her credit, Clare elevates a potential farrago into a nearly coherent, highly readable narrative. In the film, however, under the uninspired direction of Harald Zwart (his resume includes “Agent Cody Banks” and the 2010 “Karate Kid” remake), “The Mortal Instruments: City of Bones” plays like a “Scary Movie” parody.
The plot unfolds rapidly but inertly, bogged down by exposition, explanation, and ludicrous terminology. Clary (Lily Collins), a teen living in Brooklyn with her widowed mother, finds her comfortable existence shaken when she starts obsessing over a certain cryptic symbol. Then she begins to see things that other people can’t, like when a trio of Goth-styled teenagers in a club called “Pandemonium” kills someone with a magic whip and crystalline swords. In short order she’s swept up in an invisible demimonde, in which “Shadowhunters,” pale and beautiful super-powered youths like Jace (Jamie Campbell Bower) and his pals Isabelle (Jemima West) and her brother Alec (Kevin Zegers), protect an unwitting world from an army of demons. Before you can say Edward Cullen, Clary finds herself in love — and in danger.
But then things get complicated, and ridiculous. There’s a “Mortal Cup” like the Holy Grail in “Indiana Jones and the Last Crusade.” There are warlocks and witches and vampires and werewolves, whose changing loyalties and shapes are confusing but not interesting. There’s the nefarious Valentine (Jonathan Rhys Meyers), the one who dares speak his name because it’s not scary; the “Institute,” which combines Hogwarts and Xavier’s School for Gifted Youngsters; and a climax reminiscent of “Star Wars” and “Ghostbusters.” By the time it’s revealed that (spoiler alert) Bach wrote the “Goldberg Variations” to sound out demons, the hilarity inherent in “Instruments” takes over. It’s the funniest unintentional comedy since “White House Down.”