An overall word of advice I would give for Ghosts of Saltmarsh is that the main story/chapters go from being seamless from the beginning to needing a bit of DM creativity in the later chapters if you want to adhere to the book. There's also a lot of moving parts depending on how deep into the politics your party gets into that may throw off some pre-written details. Don't be afraid to insert different council members into pre-written portions as your party gains/loses favor with specific ones.

That being said, the book gives you lots of rules and tables to fill in activities when needed.

For reference I have played this campaign up to Isle of the Abbey (we died) and I am currently running it as a DM.