Orson Welles at work on 'The Magnificent Ambersons,' 1942 (public domain photo).
Marching Song, a play about the militant abolitionist John Brown co-written by Orson Welles, has just been published as a new book. It was never produced on Broadway, never published before, but did get a performance in Woodstock, N.Y.
You can read an article about it. The article is on wellesnet, "the Orson Welles web resource."