Halliburton, David. The Color of the Sky: A Study of Stephen Crane, Cambridge University Press, 1989.

Provocative study of Crane's entire body of work which emphasizes its philosophical aspects and is organized by themes rather than chronology or works. The title is taken from the opening line of "The Open Boat."

Nagel, James. Stephen Crane and Literary Impressionism, Pennsylvania State University Press, 1980.

Fascinating study which suggests that Crane applied concepts derived from the impressionist school of painting to his fiction.