I hate highlighting probably my biggest reviewing mistake of 2015, but I also cannot ignore how amazing this book is. All throughout my review of this one, I say Koch is Norwegian when he is most obviously Dutch. It even says "Translated from the Dutch by..." on the first page. D'oh! Oh well. To everyone who pointed this out, thank you.
Initially, this award was a tie between Haruki Murakami's After Dark and Herman Koch's Summer House with Swimming Pool, but the latter deserves a place somewhere else on this countdown.