It says on the cover that this is "a novel of the Promethean Age", but as far as I can tell from the blurbs for the others, this is a standalone novel set in the same world as other books, not one volume of a multi-part novel.
This is a modern urban fantasy, but it's not just another modern urban fantasy. It borrows heavily from Arthurian lore, many other folklore sources, and a number of familiar ballads, but it breaks all the stuff it borrows from into pieces, reassembles the pieces in unexpected ways, and stands the whole construct on its head. The individual characters and subplots are all fresh, and the overall theme of the novel, the conflict between the world of science and the world of magic, is viewed from an unusual angle that makes it amazingly hard to decide who the good guys really are. There's a lot to love here. However, there's also a plot with more twists and tangles than a free fall silly string fight, and frankly it's so complicated that it overwhelmed my poor little brain. Scene by scene it's coherent and compelling, but so much happens, so often unexpectedly, that trying to remember it is like trying to remember a dream.
There's a point in the middle of the book, right in the middle of a scene, where we suddenly shift from third person to first person for the main viewpoint character for the rest of the book. The rest of the book is tight enough that I'm sure this is deliberate. I think I can even understand what it's supposed to mean. But I found it very disconcerting.
I'm sure some people will think this is a truly great book, and there is justification for that. But it's just too much for me. 8 out of 10.
Even if I could remember it all, a real plot summary would run at least ten thousand words, and I'm not going to try.
The Dragon, the mother goddess who created the world, demands blood sacrifice. Every few hundred years, a recurring figure, the Dragon Prince, reappears. The Dragon Prince rises to defend a land that is being conquered. Arthur, Harold the Saxon, and Vlad Tepes (Dracula) were all Dragon Princes. To succeed, the Dragon Prince must commit atrocity and die horribly. The Merlin is another recurring figure, the personification of magic. These recurring figures are always betrayed.
In this story, the oppressed land is Faerie itself. Faerie is dying, partly because of a deal with Hell that requires a living teind (tithe) every 7 years, but mostly because the Prometheans, a group of earthly mages, are using modern technology as the basis of an ongoing series of rituals that bind and weaken Faerie. The Golden Spike, for instance, was the basis of a spell that binds the Wild Hunt. The Prometheans see Faerie as an implacable foe, and want to destroy Faerie so that no more children will be taken. Faerie really does pray on humankind. But it is also the wildness that makes the world interesting. It's law vs. chaos, and if law totally wins, the world becomes dull, grey, and safe.
Kieth is the heir of the world's werewolves and the reluctant Dragon Prince who eventually accepts his mantle. Matthew is a Promethean who was bound to his brother Kelly before Kelly was taken by the Fae, creating a link through which the Prometheans can attack Faerie directly. Kelly returned old and withered, his feet and his mind both worn away by decades of constant dancing. Carel, a black lesbian geology professor, is the Merlin. Elaine, the Seeker, is the main viewpoint character; at the start of the book she is trying to convince Carel to join the Daoine Sidhe. Kadiska is the Unseelie Seeker and seeks to seduce the Merlin to her side. And Matthew seeks to bring her to the Promethean side. By the way, Elaine is the daughter of Jane Andraste, the Promethean Archmage, and Murchaud, son of Lancelot and Morgan le Fay, become a Duke of Hell after he was taken in the teind. And Kieth and Elaine are estranged at the beginning of the book but have a son, Ian, who is thus in the line of succession of both the werewolves and the Daoine.
Elaine and Kieth reconcile as Kieth accepts the role of Dragon Prince, though they are both reluctant out of not wanting to hurt the other with their own sacrifices. Elaine figures out how to awaken Arthur and recruits Arthur as the general for the faeries. Elaine also binds the Cat Anna, the Unseelie queen, uniting all the forces that will stand against the Promethean attack. To give herself the power to withstand the Faerie throne, Elaine gives her soul to Whiskey, the Kelpie who was her bound slave but became her friend and lover. (This is when we shift from third person to first person when following Elaine.) They discover that the Dragon is bound; she could break her chain but doing so would break much of the mortal world, so she allows it to stay. But Arthur sacrifices himself and Excalibur to break the chain. The Dragon will not win the battle for their side, but she agrees to show herself to the world, to remind a world that has forgotten that such things were ever real and help shift the balance against the Prometheans. In the big battle, the Prometheans create a giant iron spike to anchor their attack. Weyland the Smith tries to destroy the spike while the Promethean army takes the field against the massed forces of faerie. Matthew comes to realize that he's been duped, that his mother planned everything that happened to Kelly including Matthew's own obsession with destroying Faerie, and gives Weyland his own blood, bound to Kelly's that made the spike, giving Weyland the power to break it. Elaine, Morgan, and Carel, meanwhile, attack the other end of the spike in Times Square. Times Square is destroyed, and all the Prometheans who went to Faerie are killed, but most of the Faerie hosts die as well, and for all of that, Faerie did not win; they moved the balance a bit and extended the stalemate. Elaine allowed the Dragon to eat her, but she didn't die; instead, she suffered unimaginable pain but gained understanding of the world. But when the Dragon returned her to life, her binding over the Cat Anna was broken. Elaine had planned to give herself and the Cat Anna to Hell, which would pay the debt in full, but no longer can compel the Cat Anna. At the end, Kieth goes instead, claiming that as Elaine's husband and the battle leader of both Daoine and Unseelie, in his person he counts as ruler of both sides and the payment to settle the debt. Maybe Elaine will rescue Kieth from Hell, qua Tam Lin; maybe she won't and that's her ultimate betrayal. But that's the end, so we don't know unless a sequel tells us.