With Tales of Berseria set to arrive on January 26th Bandai Namco has decided to drum up a bit of excitement by releasing the gaming equivalent of a unicorn - a demo! I haven't had the chance to play it myself, but what I can tell you is that the demo is around ~900MB in size, so the download should at the very least be fairly quick.
But if you need a bit more information before jumping into the demo, I would recommend you check out the recently posted "The Calamity and The Blade" trailer. It doesn't showcase much in terms of gameplay, but it does a good job of setting up the mood and characters. So if you're interested, have a look:
And if you're wondering about the system requirements, or just the state of the PC port, you'll find what you're looking for by heading over here. Long story short, Tales of Berseria will run at 60 FPS by default, support resolutions up to 4K, and come with a nice variety of options to fiddle with. I obviously can't tell you if its going to be a good PC port or not, but if the developers felt confident enough to release a demo two weeks ahead of launch that's usually a very good sign.