Sometimes it doesn’t pay to read the book. Based on the whimpers of the young women coming out of a preview screening, “Beautiful Creatures,” the movie, isn’t nearly faithful enough to “Beautiful Creatures,” the novel. Double-checking with the one person I know who’s a fan of the four-volume “Caster Chronicles” by Kami Garcia and Margaret Stohl (of which “Creatures” is the first installment), the teenage hero’s father is a crucial figure in the book but nowhere to be seen in the film. Two key characters have been mooshed into one. And there are other sins against the cosmos.

Which only proves the foolishness of expecting Hollywood to do right by a cherished source when there’s money to be made and a franchise to launch. As a “Caster Chronicles” agnostic, I kind of dug “Beautiful Creatures,” even if I, like most of you, am ready to drive a stake into the entire “My boyfriend/girlfriend is a vampire/werewolf/alien/zombie/Sasquatch” genre. The new film is porridge, but it’s porridge with a sense of humor about itself, and it clears a space for two nominally respected actors named Jeremy Irons and Emma Thompson to have a ham smackdown amid the Spanish moss. Cheap thrills, but you take what you can get in February.