Levin's work succeeds on the tiny premise, the doubt in all of us, that there must be something inhuman behind perfect facades. The book could have been longer than it is and it could have improved by more of Joanna's thoughts and the big picture of her months in Stepford. Levin was capable at least once of a character study in creeping horror (Rosemary's Baby), but I'll admit the book is just fine without it. Its quick, it was scary, and knowing the end didn't change the dread I felt at the end of the penultimate chapter.
It's an artifact, enjoy.