There is a lot of good setting and background information here, but the adventure series ignores this to go with the cliché "mad cultists running amok". The back story of the serpent people is incredibly interesting, but they are used as generic antagonists. The npc who goes missing and starts the whole thing off has an interesting (Lovecraft stolen) back story that is entirely ignored. The pirate setting is mostly ignored. This is not to say the adventure is written badly it is just an exceedingly generic adventure set in an interesting city.
The adventure also does not make the best use of its page count. At times it seems like the writer is blatantly including extraneous information to pad out the length and fit a certain page count. There is a very minor npc that only has a couple of lines and is killed off screen, but a half page sidebar is used to detail his entire life story. At another point an entire new class (cultist) is created and assigned to some low level unnamed npcs. Tellingly the class is never used again even though most of the villains in the adventure are cultists. At another point 13 pages are used to give way more information about the various NPCs at a party then would ever be needed even if one were LARPing the party. All of this means that this 120+ page adventure has less real actual content then a lot of 64 page adventures.
Again this is not a bad adventure, instead it is a mediocre adventure with an undeserved reputation and a padded page count.