Wiktionary
subliterary
a. Below the level of literature.
WordNet
subliterary
adj. not written as or intended to be literature; "subliterary works such as letters and diaries"
Usage examples of "subliterary".
The tale has relations with subliterary forms of pornography, ballad and dream, and it has not been dealt with kindly by literati.
There are those who think violence and sadism interchangeable terms, and those who regard detective fiction as subliterary on no better grounds than that it does not habitually get itself jammed up with subordinate clauses, tricky punctuation and hypothetical subjunctives.