A Conjuring of Light by V.E. Schwab, 624 pages
In the first two books of the Shades of Magic trilogy, Schwab created a series of parallel worlds centered on their different versions of London: Grey London, which is for all intents and purposes our world; Red London, a beautiful world in which magic flows freely, though not unrestrainedly; White London, which has become stark and scary through the rule of siblings who control magic with an iron fist; and Black London, which has fallen to wild dark magic and is shut off from all other places. The only people who can travel between these Londons are specific types of magicians, called Antari (easily recognizable through their one normal eye and one reflective black eyeball).
This final entry in the trilogy brings the Antari together to fight a force that has escaped Black London and is attempting to take over Red London. Though there are some elements of this story that I particularly liked (The gay non-white royalty that's not really a big deal! The tougher than nails women!), I felt a bit let down by the story as a whole. The book felt long and unwieldy, and certainly could have used another pass of proofreading, as way too many inconsistencies and typos sneaked through. It ended well enough, though, and I got to see these fantastic characters grow and mature. So it was OK.