Shadow of Mordor was an amazing game and this is mostly more of the same. It was really fun, but I think I would have liked it better if I hadn't played the first one (well, except for the story that is).
My main complaints are that there were changes to the combat system that a feel made it worse than the first game. Perks don't seem to build on each other so much as you have to chose one or another. There is more variety for sure, but I think the perk tree made you more powerful overall in the first game and was more fun. Also, the uruks can have a ton of invulnerabilities, can "adapt" if you spam them with certain attacks (which kind of sucks because sometimes it feels like the only way to beat a certain captain), and sometimes can doge virtually all of your base attacks so it can get frustrating. It makes the combat more challenging and interesting, but it can get out of hand sometimes.
Actually, the biggest complaint for me is how long each captain will talk when you encounter them. In the first game they would say a sentence or something to taunt you, but in this one they give you their freaking life story. I am in the middle of combat and then get ambushed by 3 captains and each of them has to give me a 30 second dialogue before I can just get on with the fight, which is super annoying. Also, they do the same thing before an execution so you are just anticipating the pop up the whole time so you don't mess it up. That was SUPER annoying to me.
Also, the whole kill captains and take control of the region thing is really cool, but after the first game I've kind of had my fill so it gets really repetitive.
The story is good overall, but if you are a Tolkien purest it will bother you a ton. (**Spoilers**)They make Shelob a kind of sexy shape-shifting spirit that's Sauron's ex and kind of a good guy, which is weird. The first game obviously took liberties but it ended up with a fun and interesting concept that had enough allusions to deep Tolkien lore that you could forgive it, but this game's story gets a bit out of hand to be honest.
Also, they introduce new characters that you don't really care about and spend too much time on them.
I tend to focus on the negatives because I'm sure that others will rave about the positive aspects of the game, which there are plenty of. I mostly just hope that the developers will consider this sort of feedback in the future. I would love to see the franchise expand into other parts of Middle Earth with games that have similar combat but stories that take fewer liberties with the overall Tolkien universe. Not that they can't make some things up, but it is better not to do so in a way that would have a large impact on the overall story (i.e. romance between Sauron and Shelob, adding new ringwraiths, having massive events that would absolutely have affected the stories in the actual novel).