Meh, this film was okay. Some interesting ideas in the water that aren't dwelled on much (more so than the first film). Nice photography, stronger supporting cast than the previous film, but the first half is slow and throwaway zombie fluff. Seriously zombies are not scary any more, stop doing the old "dude walks into a dark cave JUMPSCARE ZOMBIES!" thing. Movie picks itself up towards the last 45 minutes.
It does at least explain a lot of surrounding info missing from the first one, and has a satisfying twist sparking the long ending sequence.
Good atmosphere... but it suffers the same problems as the first one: meek direction, generic script, and a crap performance from the mighty talents of the charisma-vacuum that is Dylan O'Brien. A lot of the movie is just kids gawping at stuff, and some of the characters are so underdeveloped that when some potentially sad things happen to them and you're meant to feel some sort of emotion, you just end up thinking, "Who was that guy anyway?"
There are some neat setpieces though. A really neat scene in a nightclub that feels like it's been lifted from a much better and more interesting film, and made me wish the rest of the film was that good - but a great scene nonetheless.