Gemma Files's A Book of Tongues is the first in the Hexslinger sequence—no indication, as yet, of how long this sequence might be, though I suspect trilogy—and presents an intriguing world that isn't, in this volume, fully realised.

A Book of Tongues begins in 1867, two years after the end of the American Civil War. Ash Rook is a former Confederate chaplain who, hanged by the neck for mutiny and murder, has been snatched back from death by a mysterious power, the Lady of Traps and Snares to whom all hanged men belong. "Graphic physical insult can cause talent for hexation to express," according to the report prepared by the Pinkerton Agency, and Rook's innate talent has expressed itself powerfully: he can level a town, summon a whirlwind, turn a man to a pillar of salt. Unsettlingly—and surely because of his previous, albeit half-hearted, vocation of preacher—his medium of expression is Biblical quotation. The Book of Exodus, it turns out, is good for summoning a plague of ants. "In this whole wide world, there's nothing worse than a bad man who knows the Bible," Rook tells Chess (p. 210).

Edward Morrow has been employed by the Pinkertons—indeed, by Mr Pinkerton himself to go undercover and infiltrate an outlaw gang that has been terrorising the Wild West with a deadly combination of violence, robbery, and magic. Morrow's mission is not to destroy the gang, but to determine the source, nature, and extent of the power wielded by the gang's leader, the Reverend Asher Rook. In Morrow's pocket is the Manifold, an arcane device that measures hex power: at his belt, a double-barrelled eight-gauge shotgun. He'll be needing both before he's through.

The Pinkertons would very much like to turn Rook's power to its own ends. Unfortunately, so would the Lady of Traps and Snares, and she has rather more clout than any mortal agency. As quickly becomes clear—to the reader if not to the characters—the Lady is, or was, Ixchel: a Mayan goddess, with all the (literal) bloodthirstiness that implies. She has been waiting for a long time in the Sunken Ballcourt, gathering power and scheming, and now her plans are coming to fruition. Rook is warned that following the Lady is a dangerous choice, and not only for himself: his lieutenant (and lover) the mercurial, hot-tempered and vicious Chess Pargeter, is of considerable interest to Ixchel, though Rook's at a loss as to why this might be. His fine looks, perhaps, or his sharp shooting; or maybe Ixchel sees more than Rook.

A Book of Tongues does a masterful job of showing Rook's transformation from morally upstanding preacher to outlaw and magician. In parallel, Rook and Chess's relationship evolves from wary standoff to seldom-voiced but deeply felt love and devotion. (Also, to a plethora of graphic descriptions of rough sex: this may deter some readers, as may the body count and the casual, ubiquitous violence of the setting.) The focus on the emotional bond between Rook and Chess is almost claustrophobic: Morrow, with his impartial observance and his growing comprehension of Rook and Chess and the bond between them, is an essential part of the story, but doesn't have the depth of character of the two protagonists. The erosion (and Ixchel's deliberate demolition) of Rook's faith, and the gradual awakening of conscience in Chess, are more profound changes than Morrow's shifts of loyalty and respect.

However Morrow, for all his lack of backstory, may be the most likeable of the characters. Rook is tortured, Chess is cruel: of the women, Ixchel is more monster than anything, and Songbird and Grandma (one Chinese, one Navajo, both keen to warn Rook of just what he's got himself into) aren't given more exposition than their roles require.

Files has clearly put considerable thought into the mechanics of hex power, though she doesn't infodump at any point. Yet there's very little sense of the wider world in A Book of Tongues. There's a single reference to the mapping of the Chinese Hells. Chess's mother, who appears briefly, emigrated from England (and has an irritating Mockney accent to prove it). There are railroads and telegraphs. There are Native Americans, whose methodology of magic is (as one might expect) more holistic and less savage than either Rook's or Songbird's. It seems that this is a world that has always had magicians, yet is not very different to our own. Maybe, as one character theorises, it's because "ages don't meddle" magic-users can't work together without the balance of power tipping in favour of the strongest, who'll then leech power from anyone weaker who strays into their orbit, draining them and casting them aside. But maybe it's something else. The novel remains focussed on Rook and Chess, on their relationship and on the way they are used like game-pieces by higher, older, powers (I doubt their names are coincidental), but even there the narrowness of focus becomes noticeable: where are the gods of other pantheons? Or is there something unique, as yet unrevealed, about the deities of the Aztec-Maya continuum?

A Book of Tongues is distinctly part of a greater whole: there are a great many loose ends, a major cliffhanger on the last page, and a sense of scene-setting with resolution ahead—though very likely things will get much worse before they start to get better. There are also, I feel, some problems with the novel's internal structure. Non-linear narration may be the default setting of the modern novel, but a tangled timeline is less effective if the reader feels that key scenes are being elided. In particular, there's an especially jarring transition heralded by the words "four weeks later": the events of those four weeks (actually mere days in the mortal world) are told in flashback, but seem blurred and vague in comparison to the sharp snappy pace of the rest of the novel. True, it's a trip out of the world we know; true, only Ed Morrow is in any position to describe what happened on that trip, and his brand of impartial observation is ill-suited to the journey he and Chess and the others have made. Nevertheless, it's at this point that the novel begins to feel less engaging, more repetitive, less tightly structured, more like some comics than a sustained work of prose.

But while the prose works, it's wonderful. Files has a knack for writing colloquially without resort to dialect or phonetics. Whether it's snappy dialogue or Rook's stream of consciousness, the language is vivid, often expletive-laden and sharply poetic:

Gods fed and bred on the death of others, spiked higher-than-high with two parts suffering to three parts ecstasy, mirroring the blood-echo of their own. The God Who Dies but not a milkwater Hebrew Messiah, content to overspend his coin-flesh in others' service til He was good an' broke. No, this was a shell-game god whose hungers ebbed and flowed in earthquake-driven tidal waves, meting out glorious cyclical destruction. (p. 269)

A Book of Tongues is definitely promising—tantalising, even, because it sets up such a fertile scenario and hammers home the themes of love, sacrifice, and apotheosis. It remains to be seen whether subsequent volumes in the Hexslinger sequence will live up to this promise: whether Professor Asbury's Experimental Arcanistry is science or supposition, whether Ixchel's machinations will bring about the Sixth World, whether Morrow's loyalty will shift as quickly as the needle on the Manifold in his pocket. And whether the focus will pull back to show us the world in which all this is happening.

Tanya Brown lives in Surrey and has been reading and arguing about books lo these many years.