Babayaga is in some sense an historical novel, in that it is set in Paris in the late 1950s at the height of the Cold War, most of the American characters are CIA agents (some of them unwittingly) and one of the plot strands concerns a secret laboratory funded by the American military to conduct sinister biological experiments (some of them not so fictional, as we now know). But it is also a police thriller, with inspector Vidot leading a murder hunt, and it is also a fantasy novel, with a coven of Russian witches which has set itself up in Paris after the Bolshevik revolution to continue with its various forms of black and white magic.
The genres collide when the head witch turns Vidot into a flea, although this does not deter him from his undercover investigations, and the main American character falls in love with the beautiful witch, Zoya, which is the occasion for some strenuous sex scenes. After a tumult of chases across Paris, fights and explosions the Americans drive the witches out of Paris and the head witch is killed, releasing Vidot from his enchantment, but not before Zoya has destroyed the secret lab. It is all nonsense: hilarious and often witty nonsense, the antidote to all historical novels, especially conspiracy novels, that take themselves too seriously. Great fun.