Trailer probably gives you more of an idea of its (gorgeous) aesthetic than it does the gameplay, but you can see hints of how deciphering language and making sense of puzzles are at the heart of it. Wandering around reading things, soaking up context, and talking to others will expose you to glyphs that at first are incomprehensible, but get jotted down in your notebook regardless. Start to deduce what some of them mean though, and you can append your suspected meaning so that new readings displays your undertanding alongside.
Get together enough glyphs and you'll then be stirred to add a new page in your notebook, where sketches of words and concepts can then be paired up with the glyphs you think match with them. Pair up an entire page correctly and the game then validates this for you, locking in those meanings. If you've played Return of the Obra Dinn, this way in which it tests you periodically like this will feel right at home. You can absolutely brute force your way through this, but things go a lot smoother and quicker even with one other confirmed understanding.
Make enough sense of what's going on and you can likely solve some puzzles, and eventually make it on up another level of the tower and meet some new folks who... use an entirely different set of glyphs. Chances are you'll find something to help you translate a couple of basic words between languages, but the bigger challenges come with each of these new groups chasing new pursuits, be it religion, the arts, or science. Plus you'll also find they often explore new linguistic constructs - some might write the plural "men" by repetition: "man man", whereas others might have a dedicated word: "plural man" or "man plural".
The other, perhaps more surprising angle to the gameplay are the stealth sections. They're... tolerable, but definitely the weaker parts of the game. You'll find yourself snapping to cover and sliding along, having to create distractions, and moving at times when other incidental goings on provide you with cover.
In general though, I'm enjoying this a lot. Quite how I've bounced from one puzzle game (The Talos Principle) to another is beyond me, but that I've stuck with it and haven't been compelled to check a guide yet tells you it's a fairly smooth ride. It's a total looker, too.