This is a magnificent series! It has glorious prose, spectacular world-building, amazing intrigue and ... It's so good that I feel bad for not liking it. But fact is just don't. Yes, it's glorious and intricate and imaginative, to me this book was still a slog.
I'm not even sure what kept me going. Pure stubbornness and five-nines record of finishing books? (Not actually true, it's two nines and a smidgen.) A hope that it would eventually be worth it?
It definitely wasn't a desire to know what would happen to the characters from the first two books. They never seemed real to me, and I never cared for them. When they popped back into the story in this book, for shorter or longer, I never thought "Ah, I was wondering what happened to them." and at the end of the book I'm not thinking "I wonder what will happen in the next." Perhaps with one exception, but they barely appear in the book.
Only one thing, I think, could get me to read the next one, and that's a faint hope some or, highly unlikely, all of the mystery will be exposed.

If you really enjoyed the first two books, I wouldn't be surprised if you enjoy this one as well, but if you never truly related to the characters, found those to go on for too long about ... well, everything, and/or got annoyed with the sheer ornateness of it all, you should get out now.

When I'm giving it an "OK" instead of "didn't like it", it's based on it feeling less of a slog for the last 25% of the book, but there's a non-zero chance that this, at least in part, was induced by the end being in sight.