Just got the end of Turn Coat, which means I'm not up to reviewing them as I haven't read them twice, but it inspires some meditations.
It's rather a polyglot cosmology. Vampires, werewolves, the White Council are one thing. But the Fairy Courts, angels, Knights of the Cross, the loa are on a different level because of what they imply about metaphysics. More to the point, what they collectively imply about metaphysics is not logically consistent.
On the whole I think it works, by the simple expedient of working low enough that the metaphysical questions do not arise as story questions that have to be answered before the end, either because the reader's too curious or because it will actually determine the outcome of the climax.
Summer Knight on the other hand -- the Fairy Courts don't just go with the seasons. They control them. Winter Court has power during the winter, and Summer Court during the summer. Aurora's stunt, if she pulled it off, would have resulted in climate change. There had to be other Powers that Be that would object to that. If nothing else, since we have the Knights of the Cross, and this would pretty well violate, "As long as the earth lasts, seedtime and harvest, cold and heat, Summer and winter, and day and night shall not cease." they ought to be interested.
And what, pray tell, happens in the southern hemisphere?.