I've run Sleeper in the Sky several times for new and veteran Stillfleet players and it's consistently delivered an amazing introduction to what I consider the best indie TTRPG out there right now. My games have usually lasted about 4-5 hours, making it ideal for an afternoon of play, and there's so much here for the players to interact with and explore. Highly recommend if you're interested in giving Stillfleet a run for its money.