I'm several sessions in to running this now and we're having a great time.
The adventure's virtues are a ton of great locations, characters, ideas, and set pieces.
It's weakness is that the overarching plot is full of holes and doesn't feel cohesive.
The DM's toughest job will be basically adjusting or even re-writing the main storyline to create a satisfying narrative for the players. Or just using all of the cool stuff in the book to tell a completely different story.
My biggest problems with it are:
- Auril's lack of a goal
- The razor-thin narrative links between Auril, Sunblight, and Ythryn
- The adventure describes apocalyptic climate conditions that have been going on for two years and then proceeds to basically hand-wave them because, as written, said conditions are way too extreme to realistically deal with while still telling the stories the writers want to tell. (Friendly dwarven merchants want to hire you to get their stolen ingots back? No. By this point, friendly dwarven merchants have degenerated into cannibalism, died, or fled the region. Nobody cares about ingots during the apocalypse.)
- The adventure kinda sorta wants to have some kind of Shirley Jackson/mass hysteria/social control allegory with the sacrifices in the Ten Towns, but chickens out and doesn't really develop it
All of the above are quite fixable by a DM willing to deal with the challenge. And once you've dealt with that stuff, there is a LOT of good content in the book.
It helps if you don't care overmuch about adhering to Forgotten Realms lore and continuity.
For example, I solved issues 1 and 2 above by having Ythryn be the place where Auril the Netherese wizard became a god using Netherese magic many centuries ago - an event which also destroyed the city. Now the Arcane Brotherhood has discovered Ythryn's location, and Auril has taken a "nuke it from orbit" approach to the entre region to prevent others from learning Ythryn's secrets and prevent anyone from duplicating her apotheosis. Several of the factions in the region are racing to do exactly that.