There are many good communist authors but they're mainly European, and especially Russian (especially Maxim Gorky etc). But also you can bet that almost any French writer (or intellectual in general) post WWII was some kind of leftist at the very least, and Germany had some good writers too (Bertolt Brecht for example). Lots of good poets too (Ritsos, Kavadias and many others in Greece, Mayakovsky in Russia, and more I can't bother to write out now).