It means both. But I think in English "romantic" means both as well: https://en.wikipedia.org/wiki/Romantic_literature_in_English
The word "literature" is uncountable in this case.
It's countable only when it means "a subgroup/type of literature", e.g. "studies in different Asian literatures" (example from Merriam-Webster. Similar to "cheese"; it's only countable if you mean a type of cheese ("I ate two cheeses" - wrong, "I tried many cheeses in France" - OK)