They not have to be marxist specifically, but all of mine are.
My favorites are: Walter Rodney, Lenin, Anuradha Ghandy and Vijay Prishad.
I have been thinking of Red Star Over the Third World again recently, and I may decide to reread it soon.
I like Rick Riordan, author of the percy jackson series too. Childish I know, but he's the one author who didn't turn out to be a transphobic or homophobic bastard. They were my comfort reads for a long while.