We know exactly where we are at the beginning of Vellum or so we think. Guy Carter has spent his college years looking for a book, or Book, which is possibly "God's own word on every instant of eternity," dictated to the angel Metatron; or maybe a list of names of everyone who ever lived, human, angel, or devil; or possibly the actual book from which Lovecraft drew his Necronomicon. This is territory somewhere between Dan Brown and Umberto Eco: mysterious tomes, ancient conspiracies, mystical quests.
Then things turn strange. The quest, for one thing, ends in the first chapter when Carter finds the book, which is hidden in his college's Special Collection. Paging through it while the library's alarms go off all around him, he discovers that it consist of maps of the college, the town, the country, the world. The first map is slightly different from the world he knows, and they grow more so as he continues. And at some point he enters the reality of the book, so that when he leaves the library he emerges into a college town that has become utterly devoid of people.
He has, we slowly learn, entered the Vellum, the underlying reality not only of this world but of all worlds, a place of living archetypes and magic. Time and causality are fluid; the same person might appear at the battle of the Somme and in a 21st-century trailer park, and Carter's good-natured friends at the beginning show up later as hideous torturers. Soon these characters reveal their true nature as gods and other figures out of myth; The Da Vinci Code has met Finnegans Wake.
In other words, we haven't the slightest idea where we are. It's a confusing place, to say the least. Guy Carter drops out almost completely, overshadowed by the myths of Inanna and Tammuz and Prometheus. "It's not about consistency," Seamus Finnan (also known as Prometheus, and other things) says. "You can't tell the full story, the complete story, and hope to be consistent. Best you can hope for is... coherent and comprehensive."
Prometheus is right, as usual. Once you stop expecting things to make linear sense, once you get into the rhythm of the abrupt jumps in place and time, once you suppress your desire for consistency, the narrative becomes easier to follow. And a story does begin to cohere, the tale of the angel Metatron, who wants to return the universe to order and the rule of law; the fight between him and his enemies; and the struggle of a third group to stay out of the battle completely.
Still, not very much happens. Whenever we meet these characters they are doing pretty much what they did the last time, true to their archetypal nature; only the times and places change. That's the problem with the Myth of Eternal Return: it's just the same thing over and over again.
The language, though, is gorgeous, as befits an epic (and if there's a battle between groups of angels we're probably in the midst of an epic, whatever else is going on). People speak in poetry, in alliteration, in high, grand terms. Here's one character coming into a City of the Dead:
The steps of stone sweep down beneath my feet into a city of biers of bone and leather, bleached wood, paper-thin skins both dark and light; fine etched lines trace everywhere across the engraved grave city, and the stinking vapours curl in vortices and whorls as intricate as the inscriptions on all the huts of hide and banners of stitched skin.
By the end, a fair number of expectations have been overturned, including those about novel structure. Having spent an entire book with these people, we think we know who they really are and how they relate to each other - but there's still a second volume to come, and probably everything will be turned on its head once again.