Endings are hard. Especially, I think, in horror.
The Colony, by and large, is a pretty dark series. The victories the characters achieve are often measured in seconds. Safety is fleeting. Death is common.
How in the world is something like this supposed to have a satisfying ending?
By the author's own words, in a newspaper interview given years ago, there is a split in horror (and I am going to paraphrase here): there is the kind of horror that kicks you in the gut and leaves you in a gutter, and there is horror that kicks you in the gut and throws you into a hole...only to show that there is light to climb back into.
I'm not going to spoil which way the ending of The Reckoning goes, but I am sure that it is likely going to leave some people disappointed. I'm not completely sold on it myself. It did seem to come out of left field without much build up. That said it more or less worked for me, so I guess that's good enough.