Assassin's Creed Unity offers the best stealth in the series, one of the best settings, very pretty visuals, and a parkour system that feels better for those that havent gotten into the tech of the earlier games. Its also a broken mess still, and the story is not well regarded. Co-op stealth is something really special, and makes it possible to work through all the many bugs and glitches that bring the game down. If there were not these setbacks, I'd put this closer to an 8/10, but when you throw a smoke bomb and run in, only for the smoke to have just disappeared from existence and not actually throw, you dont have as good a time as you wish.
I'd say this game is worth trying out, especially if you have a friend to run the co-op missions with.