Lem wrote a couple of ostensible detective novels, "The Investigation" and "The Chain of Chance", in which he denies the reader a conventional mystery resolution entirely. In "The Chain of Chance" the culprit turns out to be a tremendously unlikely chain of coincidence (the original title was "The Cold", as in the illness, which didn't give it away completely) and "The Investigation", if I recall correctly, has no complete resolution to the mystery at all. They're not his best books, and a genre mystery reader would just feel cheated by them, but I do admire the audacity.