Believing that one of the concepts explained in SF&F books that -
1) Revolve around the presence of supernormal entities in the midst of humans, and our manipulation by them (American Gods, Word and Void trilogy, Dark Materials trilogy)- is true (and has been made public in order to throw us off-guard and make us believe that what's described cannot be possible, what with it being easily accessible and being sold as 'Fiction' (ha!)).
2) Revolve around the occurence of super-intelligent lifeforms, and their continued repression of our gaining knowledge of them (HGTG, End of Eternity)
....but not knowing which of those is true.