"The Man Who Found Out" is an excellent example of "pure cosmic horror" in that the horror derives totally from knowledge which is (in-story) so terrible that it forever blights the minds of the knowers. First Professor Ebor and then Dr. Laidlaw learn the contents of the Tablets of the Gods, and even though this information is short enough to be on two ordinary-sized tablets, it is enough to (1) induce absolute belief in its veracity and (2) utterly destroy hope in the reader. There are no monsters in the tale, nothing but Forbidden Knowledge -- which, apparently, is Forbidden with good reason.
Now to an extent Blackwood cheats. He has to cheat. Blackwood didn't know anything as terrible as the contents of the Tablets, and if he had known it, presumably the last thing he would have wanted would have been to use it to drive mad his audience. We never learn the exact contents of the Tablets, not so much as a single phrase of it.
But Blackwood doesn't totally cheat, and that's why the story is so effective.
...
====
read the rest at
http://fantasticworlds-jordan179.blogspot.com/2012/07/retro-review-of-man-who-found-out-1912.html