Aurora is a GMless, setting-neutral, multiplayer rpg about a group of characters overcoming adversity.
It's also a collaborative, crafting experience where you create your own tarot deck and then use it.
Aurora is 24 pages, with a lovely oil-painted cover, excellent layout, and some chaotic but very atmospheric backgrounds and illustrations. Visuals-wise, it's super polished.
Mechanics-wise, Aurora is broken into three connected mechanical packages. The first is a play-by-mail deck creation game. The second is a card-tile-based city builder. The third is a more conventional, character-driven roleplaying game that's nevertheless quite mechanics-light and narrative-y.
If you wanted, you could stop at any phase and have a custom tarot deck or a collaboratively built city under strain. By that same token, you could swap out Aurora's mechanics for the third part and replace them with something more dungeon-crawl-y. Aurora actively encourages this, and it gives you a lot of guidance throughout on how to hack it.
Overall, if you like storytelling games, this is a heck of an engine. It delivers three different experiences, any of which could be a full game in its own right, and any of which could be hacked and adapted to your own purposes.
If you're here for crunch, Aurora does not provide a ton on that front, and you'll have to add your own. But with that said, Aurora is extremely well put together, and it may be worth a look even if it's outside of what you'd usually play.