Is there a word / term for fiction books that use fake non-fictional forms, pretending that they’re real? (Also, i’m looking for suggestions)

examples: multiple Borges and Lovecraft stories Lem's "A Perfect Vacuum" (fake reviews) Pavic's "A Dictionary Of The Khazars" (fake encyclopedia/lexicon) various texts pretending to be academic essays, including footnotes etc. by SurrealFishMoment