I have it. It's a beautiful, fun game that is a lot deeper in strategy than it looks on the surface.
It's a different game than Skyward Collapse, but it does has a lot of similarities in concept and theme. Saying which one is "better" would be a bit unfair because Skyward is not finished yet, but I will say that Reus has systems that Skyward dropped (score and challenges), and Reus implements them very elegant way (the game is built around them).
The game plays in real time, and you play the game over an era. An era is essentially a timed session from a completely blank world until the clock runs out. During this era, you seek to build up the "prosperity" of your world as much as you can. Completely specific objectives will unlock new things and advance your level. It can even open up longer timed sessions.
Prosperity is basically your score, and it's a straight up sum of all your food, tech, and wealth of all of your towns. You build the prosperity of your town by placing various resources within their borders. The borders are very tight (like 5-6 spaces), but they do expand a bit as the towns grow in prosperity (and the really cool thing is they do actually advance, you can see the townfolk advance from a nomadic settlement all the way to an imperial age city). You have to take advantage of synergies of the resources you place to make them give bonus resources. Your giants can place different 'aspects' on them, which can make the resources upgrade to a new type. An upgraded resource is not a direct buff to the last, it's actually a brand new resource with brand new synergies of it's own. Luckily, it's very simple to experiment and place things, because all it will cost you is a bit of time. It's a bit of a puzzle game in some aspects.
The resources you place down will determine the 'maximum' that town can reach in that resource, and the town will grow toward it (so if you place down stuff that provides 15 food, they won't immediately HAVE 15 food). It will tick up a lot faster if there is a greater difference between current and max. A caveat is that if a town is growing too fast, they will start to get greedy. When they get greedy, they will start deciding that they want to go capture other towns. You can manage this by increasing the awe and danger levels of the town through which resources you place. Awe is a simple reduction of greed, but not as easy to get. Danger, when increased to a certain level, will basically put the town into a "we're too busy fending off wolves to deal with being greedy". Increase the danger too much and they go into "oh god the wolves are eating us" mode. I've once just threw an earthquake under them and leveled the area to start over, so that's a way of dealing with it too!
Based on the biome of the town and the type of resources they have, different projects will get created. These projects take up a random space (which can get annoying with your synergies), but they provide huge bonuses to resources. They require you to meet certain resource levels in specific types to be completed. As the town grows, they will upgrade them into higher level projects. Some of the projects require special objectives, like a sacrificial alter that will require the complete destruction of a rival town). When a project is completed, the town will provide an ambassador, which you can have one of your giants pick up and carry around on their shoulder. The ambassadors provide a new ability to that giant, and they are effectively how you "level up" each giant. The ability provided depends on the giant and the type of ambassador.
I haven't gotten far enough to see it's effects, but there is a level of each town in how much they basically 'respect' your giants. It seems to stay at good levels of you are doing stuff to them. I've heard from another player that they had a town send over a whole bunch of men and slay one of their giants with spears, so I guess you can't ignore a specific town for too long.
Did I mention the art direction is just gorgeous?
If you have any more specific questions, I'll do my best to answer them.
