Naomi Klein's Doppelganger is a fascinating book; I wrote about it on Medium last month.

Right now, separately, I'm drawn to your mention of certainty. It makes me think of something from a new perspective.

Conspiracy theorists often believe contradictory hypotheses. They're sure that there is a conspiracy, but they're open to many possibilities of exactly what that conspiracy might be, including mutually exclusive options (e.g., the event was perpetrated for sinister motives, or was an elaborately staged hoax, or never occurred at all), all of which they may maintain in the same breath.

On which note, I remember Dale Stromberg's essay earlier this year on what he calls "the veiled known," which is a story that implies there is a known truth, but the narrative deliberately conceals that truth from the reader. The reader feels motivated to stick with the story to try to approach the truth.

https://medium.com/@dale.stromberg/the-veiled-known-cf68a99ec4d2

Some fiction works this way, as Dale points out, and I also think conspiracy theories work this way. Insofar as conspiracy theories are false by definition, they contain no truth for the reader to grasp. (Nor is there anything to be known, under classical definitions of knowledge that depend on belief in a true statement.) But someone prone to conspiracy theories feels certain there is a discoverable fact somewhere deep inside the tangled knot: a veiled to-be-known.