Don't get me wrong, it's not terrible. It's not Insurgent-level nonsense. It's just that the first book was SO GOOD. I really, really liked it so much. But I feel like he had this great idea (alien apocalypse, world is ending, do we fight back and how do we do it? etc.), and now he's stuck with, ok how do I move this forward? How do I make that great idea from book #1 make sense.
A lot like the Insurgent crap, actually. So he's spending a lot of time talking (via the characters) about what the waves are, and why. Why are the aliens choosing this way to do us in? Why not a giant bomb or something with a 100% kill rate?
There's a lot of navel gazing, as we say around these parts.
I'm going to keep reading, of course. I loved book #1 that much (and liked #2 ok, too), that I need to see it through. I was just hoping for something that would make it all make sense. Not this convoluted navel gazing that I'm starting to suspect he's going to continue.
I can't wait to have a spoiler post dissecting it once a few of us have finished.
ETA: Allegiant. Allegiant was the crappy 3rd book in that series.