Publishers Weekly:

In Nykänen’s complex third mystery featuring Helsinki cop Ariel Kafka to be translated into English (after 2014’s Behind God’s Back), Kafka is summoned to an apartment where the naked corpse of Roosa Nevala, who had a history of psychiatric problems, lies on a sofa, her back adorned with ominous Biblical citations. The case becomes even more bizarre when the medical examiner recognizes her as the same woman who fatally overdosed on sedatives the day before and was brought to his morgue to be autopsied. Kafka is further unsettled when a letter to him is found under Nevala’s body, signed by “The Adorner of the Sacred Vault,” who refers to a holy ceremony that will end only after an evil dragon is slain. When Nevala’s corpse vanishes again, Kafka is called by the thief, who advises him to “follow the signs of fire” to learn the truth. The solution to the subsequent murders that Kafka eventually learns of is particularly clever, and Nykänen is careful to plant the clues to whodunit and why fairly. Readers will look forward to Kafka’s next outing. (Mar) 

Kirkus:

The third case for Lt. Ariel Kafka, of Helsinki's Violent Crimes Unit, begins with a twice-disappearing corpse and just gets wilder. It doesn't take a minute for medical examiner Dr. Esko Vuorio to identify the body found in an apartment in the Töölö district: it's psychiatric patient Roosa Nevala. And Vuorio should know, because he examined her only yesterday in the city morgue, from which her body has been stolen, laid out, and adorned with scriptural references. There's no sign of violence but many signs of weirdness, not the least of which is the vanishing of Roosa's body from the morgue a second time so that it can be immolated in a forest outside the city. Roosa's boyfriend, Reijo "Reka" Laurén, a cellist with a criminal past who's worked most recently at a funeral home, is clearly implicated, since he lived in the apartment her corpse visited briefly. But Laurén, who in his school days at the repressive Daybreak Academy belonged to a secret society called the Sacred Vault, insists he's not a killer.  Maybe Reka hasn't killed Roosa, but the trail that begins at Daybreak Academy leads to an awful lot of other suspicious deaths. Is Reka seeking revenge on Vesa Särkijärvi, the old teacher who's been accused of abusing many of the boys in his care, and other figures who may have covered up his assaults? Or has someone else battened on to the ancient grievance Reka shares with several other schoolmates, some of them slated for their own homicidal ends, for an even more sinister purpose? Less distinctively woolly than Behind God's Back (2014) but just as intricate in its layers upon layers of corruption, murder, suspect cops and public officials, and seriously dirty secrets.

Great review in New York Journal of Books:

 Nykänen’s writing style is clean, direct, and unadorned. As with Michael Connelly, his skill with words seems to have been well-honed through years of experience as a journalist.’“Scandinavian noir is an enduring subgenre in contemporary crime fiction, and we’re constantly made aware by North American publishers of the latest English translation of novels from Nesbø, Läckberg, or Sigurđardóttir. Harri Nykänen, on the other hand, has more or less flown under the radar to this point. Perhaps his Ariel Kafka series, and Holy Ceremony in particular, should begin to attract the attention Nykänen deserves in this hemisphere of the crime fiction world.”