Conjure Wife

In this novel, originally published in 1943 in "Unknown Worlds" magazine, a college professor discovers that his wife has been practicing magic unbeknownst to him. Though she says that her spells have been protecting him, he convinces her to give it up. Sure enough, their lives begin to fall apart as it becomes clear that more than one magic force is working on the campus, and the professor finds that he will have to abandon some part of his rational mind if they are to survive.