This is really good! I've run it twice now for two different groups and the tension always mounts as intended. The art is really cool (I reccomend sharing some of it with your players at tense moments) and the Abyss is tons of fun.
My only gripe is that everything in this module wants to hurt the players. The things in the dungeon are super interesting, don't get me wrong, but when interacting with it leads to punishment instead of reward 99% of the time, the players tend to shut down and just avoid everything. The only reason they don't leave is because the dungeon locks them in which is kind of lame.
But, this adventure is definitely still worth it!