The fascination with the idea of human automata or robots goes back to the earliest days of modern technology. In the early 1800's, Henri Maillardet built astonishing automata, including one which could write poetry and draw. This figure, amazingly, was found in a state of disrepair after having been damaged in a fire; on its being restored and wound up, it made a number of drawings, including one one under which it wrote "Ecrit par L'Automate de Maillardet" -- Written by the Automaton of Maillardet -- in a sense, it identified itself.
The quest in more modern times has been to create a robot which is as similar in its outward capabilities as a human being, and yet most of its fictional and film incarnations have been hostile rather than kind: cyborgs such as the Terminator, organic humanoids such as the Replicants in Ridley Scott's Bladerunner, or the Borg of Star Trek, whose famous taglines are "resistance is futile," and "you will be assimilated." Friendly robots have not fared so well; the best, such as Robin Williams' Bicentennial Man, have been vaguely pathetic in their never-ending quest to reach a humanity that is denied them.
Levin's genius -- and the genius of the 1974 film version, starring Katharine Ross -- to imagine robots who are nothing if not built to please -- men, that is -- but whose ultimate significance to the women they replace is a total loss of identity, followed by a death that will never be reported in the Stepford Chronicle. They're entirely technological, but in other respects much like their organic counterparts in Invasion of the Body Snatchers.
There are a few interesting differences between the book and the film, most significantly its ending, a fade-to-black that suggests that the knife goes in a rather different place. The book also introduces a black couple new to Stepford, Ruthanne (a children's book author) and her husband, Royal. It's a feint -- sexism trumps race, and while Ruthanne is useful to the book's last pages (it's through her eyes that we see Joanna's replacement), there's a strong implication that she, too, will soon be Stepfordized.
As an aside, the novel explicitly mentions the urban legend about the Abraham Lincoln animatronic (designed by Disney engineers for the 1964 World's Fair) going 'crazy.' It didn't, but a frequently posted online video shows that it had other, equally bizarre, troubles. The adventuresome might also check out the TV sequels, Revenge of the Stepford Wives and The Stepford Children -- for even more animatronic weirdness.