To me this game is like The Witcher 3 and God of war 4 had a baby.
Simply put it has an amazing open world that is teeming with life with interesting and fairly diverse side quests. Coupled with very solid combat mechanics.
I have not completed the main game yet(At the latter stages of Act 3) and this game is long, but does not feel like a slog(Looking at you Assassin's Creed).
The only negative I can really think of is the lack of a memorable soundtrack. The music is just fine.