As someone who's never played the original NieR or Drakengard titles, I can assure you that this sequel, NieR:Automata, requires no prior knowledge of the NieR/Drakengard series to be played.
With that said, NieR:Automata is easily one of the greatest titles that I've played in the last 5 or so years, and likely the by-far top contender for my own personal game of the year.
Despite the mainstream attention that this game deserves, but HASN'T gotten, NieR:Automata is still of much higher quality than a majority of all AAA games created these days, and that's in all regards, including art, animation, soundtrack, voice acting, gameplay, story, and direction. And this is all despite the fact that it was only 2 years ago when it was announced that a sequel for NieR would be in the making, and despite the fact that the budget for the title isn't considered high enough to be called a AAA game itself by a majority of the gaming community's standards (though many, including myself, still consider it a AAA game just because of how the content itself ALL fits the criteria of being one outside of the logistics).
The primary thing that stands out within NieR:Automata is the gameplay. It starts out as a typical free-roam RPG-style hack'n'slash with a really immersive combat system similar to that of Bayonetta (also a Platinum title), with lots of mobility, multiple melee weapons, the ability to aim and shoot bullets, being rewarded graciously for dodging attacks, and being able to chain together air attacks without being able to go too far without having to nosedive into the ground to finish off your combo. The fluidity and design of every combat method is absolutely beautiful, and the combat system itself is the very definition of perfect for many people, myself included.
However, the main quirk of this game is that you won't be doing the exact same thing for the entirety of the game, something director Yoko Taro even paid mind to when discussing why he decided to direct the NieR series as a whole in the first place. Throughout the game, you'll see seamless, unforced transitions to differing styles of play, from the typical free-roam style to a platformer style, eventually to fighting bosses that fling hundreds of projectiles in all directions at once that make the game feel like a traditional bullet hell, and even seamless transitions from gameplay to cutscene, which are all extremely interesting and despite being entirely pre-rendered, still use the same 3D models and system as the game itself (which using a different style usually isn't a big deal to most people, but the transitions can sometimes feel forced that way).
And while I won't discuss it very much for spoiler reasons, you'll eventually be able to play as multiple characters, which makes the game in general a whole lot more fun. There's also a bunch of really fun Easter eggs to discover, most of them being in the form of funny game endings that cause a cutscene to play that features sarcastic text followed by the credits rolling extremely fast, and the game ending and requiring you to load your last save file and play it where you last saved, the only difference between then and now being that you unlocked a new ending (which the game keeps track of).
There's also many other styles of combat, such as flight units and a minigame that revolves around hacking, meaning that you can't really be bored playing this game just because of how there's so much to do in it.
This game follows typical Japanese RPG (JRPG) formulas with how you can level yourself up and progress through upgrades and obtaining new weapons which have different capabilities and functions. There's also lots of monster and boss encounters, but unlike in some games within other popular franchises, such as Final Fantasy and Tales, the NPC encounters aren't random, and are all on the stage with you to choose when to fight them (there's almost always foreshadowing when it comes to bosses as well). This style of gameplay works very well with the game at hand due to the free-roam aspects and the fact that combat is the main focus here.
The world itself is somewhat large, but not massive like in some other games (specifically within the Final Fantasy and Tales series).
The art is absolutely amazing and perfect in every regard, with the 3D models of the characters being among some of the best looking ones that I've ever seen. The soundtrack itself is also among one of the very greatest I've ever heard in any video game, possible THE very greatest. It's one I've listened to numerous times on its own, which is something I VERY rarely do with soundtracks in general, not even limited to just game soundtracks.
My only major complaint with the game is one that's easy to look over: the second route is boring. I won't get too deep into it due to spoiler reasons as well, but you basically need to complete the same campaign twice, with the second time around being with a far more boring character. However, it's something I can look over very easily simply because of how quickly you can breeze through it, as there's very few new cutscenes and most can be skipped. Beyond that, every single minute of the game is extremely fun and something you're more than likely going to want to play through more than once.
All in all, amazing game that you should without a doubt pick up if you're into the free-roam JRPG style of gameplay, with an immersive hands-on fast-paced combat system, lots of diversity among how the gameplay is presented, alongside amazing art and an absolutely breathtaking soundtrack. And heck, even if you aren't, I'd still recommend giving it a try simply because this is a game that comes so close to pure perfection and will likely end up being my game of the year for 2017, as I truly cannot imagine anything surpassing it in this day and age.
Buy NieR:Automata, you won't regret it.