At first glance, The Handmaid's Tale seems to fit well into the genre of science fiction, with its new social caste system, alternate view of the future, and abandonment of technology for primitive ceremonial systems. However, the author herself disagrees with this characterization. In 2005 Atwood presented the argument that her work is speculative fiction rather than science fiction, and that the two genres are really different:
I like to make a distinction between science fiction proper and speculative fiction. For me, the science fiction label belongs on books with things in them that we can't yet do, such as going through a wormhole in space to another universe; and speculative fiction means a work that employs the means already to hand, such as DNA identification and credit cards, and that takes place on Planet Earth. (source)
Many of the book's plot elements also fit well into the genre of dystopian literature. In a dystopia, we can usually find a society that has become all kinds of wrong, in direct contrast to a utopia, or a perfect society. Like many totalitarian states, the Republic of Gilead starts out as an envisioned utopia by a select few: a remade world where lower-class women will provide upper-class couples with children, and the human race can feel confident about producing future generations. Yet the vast majority of the characters we meet are oppressed by this world, and its strict attention to violence, death, and conformity highlight the ways in which it is a far from perfect place.
Atwood points to this idea of utopia or dystopia specifically in an exchange between the narrator and Moira that takes place before the Republic takes over:
[The narrator] said there was more than one way of living with your head in the sand and that if Moira thought she could create Utopia by shutting herself up in a women-only enclave she was sadly mistaken. (28.7)
Female characters are frequently told in The Handmaid's Tale how much safer, more protected and better off they are. By themselves, those are utopian characteristics, but in this context, they're anything but.