Heidegger's antecedents

I think there is a book about Heidegger called The Rumour of the Hidden King. Heidegger appeared on the philosophical scene as if from nowhere. But he certainly has antecedents and forbears, and I think getting familiar with them is indispensable for understanding Heidegger: Husserl certainly; the dominant Neo-Kantians of the time (Cassirer included? certainly Natorp); Dilthey; Graf von Yorck; but also Karl Barth, and his appropriation of Kierkegaard; therefore Hegel; and certainly Scotus.