I ran this as a one-shot scaled to a 5th level 3-person party, and I loved running it! But more importantly, the group loved playing it. Some of the players were especially fond of the focus on mystery and puzzles rather than fights, so the ending was very fitting.
Future players and/or DMs should be aware of the potential for a long session.
Personally, our session lasted for a long time.
Also, one of the players were expecting a big "boss fight" in the end, but luckily found joy in burning down the house with the "fireball-in-a-glass-sphere" instead.
I will definitely try out more of this creators products in the future and I am sure, my group will enjoy it as much as this one.