The Summoner by Layton Green
"Grey was no saint, but [...] he stuck to the vices that only affected himself" (20)
When William Addison, retired head on Consular Affairs at the US Embassy in Zimbabwe, disappears under mysterious circumstances, Zimbabwean officials refuse to allow the Ambassador to bring in federal agents to investigate. That's when Dominic Grey, a diplomatic security agent whose time is usually spent escorting government officials around the capital and dealing with passport and visa fraud, is put on the case.
Grey will be shadowed by Nya Mashumba from Zimbabwe's Ministry of Foreign Affairs during the investigation. Though Nya is easy of the eyes, she's reticent to the point that Grey suspects that she may be withholding important information about the case. His only other assistance comes in the form of an expert the Ambassador brought in from Interpol. Viktor Radek is a professor of religious phenomenology and an expert on cults. The deeper Grey and Nya delve into the mystery of Addison's disappearance and the people behind it, the more they realize just how much they need Radek's expertise and the closer they come to becoming targets themselves.
The titular character, N'anga ("the summoner" in Shona), is a babalawo (priest) practicing a perverted version of Juju, the traditional Yoruba religion. He uses human torture and sacrifice to garner favor with the most malevolent of Orisa spirits. Because of this The Summoner is not for the faint of heart. I'm a bit on the squeamish side and had to skim through some of the more disturbing passages.
While I do read this type of book occasionally, the thriller genre is not one that I particularly favor (and I generally prefer my mysteries on the cozy end of the spectrum). I did think The Summoner was very well done. The novel's protagonist is a complex and compelling character with an interesting backstory. I appreciated how Green was able to incorporate the culture, history, and current political milieu of Zimbabwe and Nigeria into the story without being heavy-handed. I can think of quite a few people to whom I'd recommend this novel.
The Summoner is the first book in a series, which I assume will follow Dominic Grey as he investigates other crimes committed by fringe religious groups. The way things are left at the conclusion of the The Summoner, it seems that the novel's two most interesting secondary characters (Radek and Nya) will be reappearing in future installments.