There is a treasure trove of old WOR air checks and club appearances available on the Internet (flicklives.com is a good place to start). Check out his reading of Robert Service poems at Christmas time (The Shooting of Dan McGrew, The Cremation of Sam McGee, The Ballad of Blasphemous Bill) - all classic stuff read by a master. I've got other sites bookmarked at home if you're interested.
As for books, after In God We Trust, I would recommend Wanda Hickey's Night of Golden Memories (and Other Disasters), and Fist Full of Fig Newtons (some terrific army stories in there).
Excelsior!
My mom always said one of the regrets of her life is not going to hear him in NYC. From what I understand he used to do readings in the Village.