What The Little Hours has going for it is this: it's an anachronistic comedy set in the 14th century. If it proves anything, it's that the simplest of settings can be turned into comedy gold. It's just not as golden as it otherwise perhaps could have been.
To clarify, the only particularly noticeable anachronism here is in the way the characters speak to each other. Alison Brie, Aubrey Plaza and Kate Micucci all play nuns in a convent, each presumably there for different reasons -- this was in a time when all manner of circumstances brought women to live in convents; it wasn't all just "a calling" to God. Brie's character, Alessandra, is literally waiting -- in vain -- for a suitor to come along and take her away from there. Her father, in a cameo by Paul Riser, is one of this church's largest benefactors.
And there's something weirdly feminist about the presentation of the story here. I don't mean that as a criticism per se; it just feels odd, as presented in this way. This is very much an ensemble cast, in which women get by far the most screen time, as well as lines. The women in this convent must contend with their own desires when the priest (John C. Reilly) brings in a servant on the run (Dave Franco) who had been having an affair with the wife (Lauren Weedman) of his master (Nick Offerman). For his own safety -- from the nuns more than from his master -- the servant is presented as a "deaf mute." It is established very early on that the nuns don't take kindly to their gardener deigning to speak to them. They respond with foul-mouthed hostility that is as amusing as it is befuddling.
The title credits, which use a font I've never seen before but still managers to look seventies-retro, indicate to us this story is based on The Decameron, by 14th-century Italian author Giovanni Boccaccio. So there is some very, very old source material here -- although the writing credit otherwise goes solely to Jeff Baena, who also directed. When the story begins, it's pretty simplistic: we see one of the nuns guiding a donkey that we later learned escaped the grounds back to its home. Eventually things get complicated enough that the story incorporates fluid sexuality, romantic deceit, and even a rather strong dash of witchcraft.
I'll give The Little Hours credit for that: few movies are less predictable. And it does have plenty of laughs, a large percentage of which come from the way these characters talk to each other in the context of their 14th-century existence. But it never quite coalesces as a solid story. There's a persistent unevenness here that's difficult to shake. It's like a truly fascinating experiment -- something you really can't look away from, from beginning to end, and that alone makes it arguably worth a look. But in the end, as relatively fun as it is, it really doesn't quite add up to the sum of its parts.