From hands of Graham Walmsley, this adventure is a good piece of Lovecraftian Horror. If you played adventures before, this holds one or two surprises for you, I hope you kept that campaign notes. The mystery unweaves as Investigators find clues and are driven into madness. If whole series was a novel, It would be a good example of Lovecraftian Horror.
(Maybe it is, you know. Stealing Cthulhu was a good reading. No wonder he get a really good kick-start(er))
There is almost everything a Narrator wants, and there is nothing unwanted. Maybe some grotesque descriptions could help but usually, from my experiences, Narrators don't like them too much. Usually, they use their own depictions so I don't think this should be considered as minus. There is personality notes for each important NPCs that investigators may interact and from nature of Trail of Cthulhu System there is a lot of clues for them to solve.
Just turn off the lights, lit candles, put a soft but gothic music in low voice to background and start your investigation.
[5 of 5 Stars!]