Robert O. Paxton, in "The Anatomy of Fascism" writes:
"It was long believed that the Nazis themselves set the fire and them framed a dim-witted Dutch communist youth found on the premises, Marinus van der Lubbe, in order to persuade the public to accept extreme anticommunist measures. Today most historians believe that van der Lubbe really lit the fire, and that Hitler and his associates, taken by surprise, really believed a communist coup had begun. Enough Germans shared their panic to give the Nazis almost unlimited leeway."
Cited references: Fritz Tobias, Der Reichtagsbrand: Legende und Wirklichkeit (Rastatt-Baden: Grote, 1962) and Hans Mommsen: "The Reichstag Fire and its Political Consequences," in Holborn, ed., Republic to Reich: The Making of the Nazi Revolution (New York: Pantheon, 1972), pp. 129-222 and in Henry A. Turner, Junior, Jr ., Nazism and The Third Reich, (New York: Franklin Watts, 1972), pp. 109-50 (orig. pub., 1964).