I'd mention the ending but it seems to be a common complaint of the series. Also, this was only my second venture into YA. I started reading Abercrombie's Shattered Sea trilogy without even realizing it was YA (I hadn't realized just how graphic the genre could be, Reckoners included). Anyways, other than the unsatisfying ending, I find myself more interested in what would come next more so than everything I've already read.
I would much rather see how this world that has existed among cruel and heartless Epics would react and adapt to them being heroes, especially as human governments start rising again. It is hard to imagine that they would openly welcome heroic Epics, even new Epics who appear post-Calamity (I imagine that all of his power sets would remain and recycle among humans, pretty much creating a world of superpowers among humans without the inevitable corruption bit).
Also, this might seem strange since I read the entire trilogy but I didn't really like David. For one, I wasn't aware it was written in first-person when I bought it or I may have waited. Regardless, I didn't really like Dave most of the time and his personality seemed... weird. His whole shtick of being bad at metaphors made me smile here and there and I guess it was meant to be funny but most of the time I just groaned when I read it (and not in a good way like when hearing a corny pun). He did have his moments, though where I did connect with him and actually care about him such as the scene where he recalled riding bikes with his dad.
With all that said, I still enjoyed the series. This is one of the few stories I've read in which the plot made me want to keep reading more so than the character, even if the ending flopped a little. I loved the idea of ordinary humans fighting against superpowers (with minimal superpower aid of their own). I also loved all of the unique Epic weaknesses and power-sets. These power-sets are an awesome example of why and how Brandons is so good at creating magic systems. He takes a lot of old, recycled power sets and adds an interesting twist, usually in the coupling of strange and off-the-wall weaknesses and limitations.
People keep talking about how they want a movie or a TV series but I'd like to see a comic book version (or continuation, as mentioned above). A table-top RPG would be pretty cool, too.