One of the reasons that I really liked this series at the out-set was that while it was a standard-as-all-heck sword & sorcery/epic type story, Martin wrote good characters that I liked and genuinely cared about. And even in this last installment, it's the little personal touches of the story between the characters that I enjoy the best.
Unfortunately, they're rather few and far between as the story, overall, focuses on the war being fought on multiple fronts.
One of the downfalls of our characters being spread all over - aside from the lack of personal touches - is the fact that we jump between 5 or 6 different perspectives, and as soon as things start getting good, we jump to someone else.
More than that, though, is the fact that our characters have little to know way to communicate with each other, so we see each group sort of have to learn the same things that you already watched the other groups already learn. And while it makes sense to the story for all the groups to have certain information, it gets kind of tedious to have to keep reading the same stuff over and over again.
And while the battles were sometimes cool, they felt mostly repetitive, and it was kind of annoying that it was just "ooh, here's the newest and baddest magical thing you have to fight against" and then, against the odds, people win, and then "ok, no, here's the newest and baddest magical thing you have to fight against".
*sigh*
There were some moments were it shined (Gethin was a nice addition, though I would've liked to see him interact more with Berry, Jonmarc's thoughts while on the battleground and missing the birth of his children was good, I liked the Aidane and Kolin storyline until Aidane started acting so stupid), but, overall, it just didn't live up to earlier installments in the series. I missed Carina and Calloway a lot, and Tris' parts, which were often my favorite in past installments, seemed to fall flat here - even though they were, arguably, some of the more intense and interesting. And after all the set-up, the climax was just so rushed and sort of unsatisfying, and a lot of the magical problems were resolved a bit too patly.
I don't know - just, overall, I felt like Martin was relying on our connections with the characters from earlier books in the series instead of putting any effort into it this go around. (I will say, though, that she's pretty good at reminding you of things that happened in past installments without doing huge info-dumps.)
Anyway, I didn't hate it and it was a pretty fast read, considering the size, but Fallen Kings doesn't hold a candle to the Necromancer cycle and it's kind of a pity that the end of the Kings cycle was so meh.
It was also kind of annoying that the ending read a lot like the set-up for the next arc in the series, which is obviously going to involve the children that everyone's having. Bit too heavy-handed with the hooks for the next arc in the series, there.