“A literature” - the count noun - is a reified collection of literature - the mass noun. There are as many literatures as you care to reify.
The literature of child-emancipation court documents.
The literature of MCU fan-fic.
The literature of toilet bowl cleaner warning statements.
The literature of arguments about the meaning of the count-noun “literature”.
Take any set of written material, conceive of it as a thing, give it a pithy name and viola! you have a literature.
