This final Alex Verus book is almost all magical battle as the Light Council goes to war against Anne (Alex's lover) who has been possessed by a powerful jinn-like thing with an army of jinn to call on. Alex signs up for the fight with the intention of rescuing Anne, while the Council wants her deader than dead. Swinging into the fight in the side of the council is Richard Drakh, dark mage and once Alex's apprentice master. Alex doesn't trust him, of course. Richard has been his enemy all through this series. You just know that the final showdown will be in here somewhere - and you'd be right.
The council, rife with internal politicking, still doesn't trust Alex - its only one book ago that they had a kill order out on him, and some of the mages he used to class as freinds are no longer on his side. Luna, his one-time apprentice, now a mage in her own right, is along for the fight and also hoping to rescue their friend, Variam (also possessed).
There's one problem that might prove insurmountable - Alex knows he's dying. The immensely powerful Fateweaver has replaced his missing hand, which gives him a real edge as it helps him to nudge the futures he can see in the direction he wants them to go, but the Fateweaver is gradually taking over Alex's body creeping up his arm to his shoulder, and when it reaches his heart, that will be that. But the Fateweaver was made for battles such as this, and so Alex ends up in the forefront of the fight.
Alex has come a long way in twelve books. He started out as a mild magic shop owner in Camden Town, but circumstances led him to gather a few trusted friends around him and to cross swords with the Council and with Richard Drakh. He's always tried to be on the side of the light, but he's done a lot of dark things in order to save himself and those he loves. How will it all turn out? Though I got a little tired of all the battle sequences after a while, I found it a satisfactory end to the whole series.