Laurus can be described as historical fiction, it takes place in 15th century Russia, but that gives the wrong impression about the contents. It does not simply tell a medieval story, it tells the story in a medieval way.
The mental barriers between us and the past are high. The modern mentality is very different from the primitive, ancient, or medieval one, just as these are different from each other. The medieval or ancient person experienced the world differently. Time for the ancient and primitive worlds was cyclical, for the modern it is linear. The medieval person understood time as a little of both: Time is linear because the world was created and was expected to end, but God was the timeless center of all reality, and time as experienced by creatures was a relative thing, an aspect of their imperfection. The closer one drew to God, the less time mattered, as in the liturgy. Liturgy allowed one to step outside of time and participate in the events of the life of Christ, which themselves were expressions of the timeless inner life of the Trinity.
But Medieval time was also cyclical. The liturgical year recreated, in a sense, both the life of Christ and the history of the world. History played out familiar patterns which the chroniclers noted by conflating characters from different eras, or lifting stories from a similar tale because of some moral analogy: they were bad historians by our standards, but not by theirs because they put a different value on time. Consider the fact that medieval time was also, in a sense, fragmented. Because news travelled slowly (or mostly didn’t travel), and most people were illiterate, and because a person could start an entirely new life by moving to a different village, there existed little ecosystems of time independently of one another. This made the patterns of the story all the more important. What linked the various times into a coherent whole was their conformity to type and their moral analogies, not their linear relationships, which were often unknowable.
So in Laurus it is not a big deal if sections are routinely lifted from the Old Slavonic liturgy, or if a character slips in and out of archaic speech and modern slang. A 15th century character might note the ugliness of plastic refuse uncovered by melting snow, because it is simply part of the experience of spring. Time being relative, a man might have the ability to see far into the future, be able to describe in minute detail a tale of missed love in St Petersburg that will take place 1971, while holding in his head the simultaneous conviction that the world will end in 1492. (And if you stop to think, a world, the medieval one, really did end in 1492.) The result is a novel that (let me say this in italics ’cause it is important) feels more historically accurate as a result of its anachronisms. It feels more medieval because it attempts to get deep inside the medieval head.
It is often funny. And it is beautiful: seasons, landscapes, cities and nations, and people are lovingly described. And it is violent: theft, beatings, horrible deaths from pestilence, accidents, childbirth, and murder are described in the same detail.
I recommend it.