Warrior Cats road to immortality, it's a fangame for a book series but at the beginning you can ask a few questions about the world so I think even those unfamiliar with the series can play it. It has a lot of endings (8, but not all choices you make along the way impact the ending, so you can finish the game twice with the same ending but different circumstances, e.g someone being dead), side quests/events and your choices matter a lot. It's a game you could play every day for weeks and still find something new. Overall, I think I've played it 60+ times and it's really great. Huge recommendation to everyone who enjoys story-driven RPGs with choices that matter.
There's only one Act out and it's been like that for the past 8 years. The development for next acts is slow, but the developer is still active and working on the game. The ending of the first act doesn't leave many things 'hanging' or unanswered, so it doesn't feel like you're on a cliffhanger.