Boulby, Mark, Hermann Hesse: His Mind and Art, Cornell University Press, 1967, pp. 159-205.

As of 2006, this was one of the most detailed readings available. Boulby discusses such topics as the significance of music for the novel's structure and theme; he views the novel as an optimistic one in which faith imposes order on chaos.

Mileck, Joseph, Hermann Hesse: Life and Art, University of California Press, 1978, pp. 174-97.

Mileck discusses such topics as the autobiographical elements in Steppenwolf. He doubts that Hesse himself took hallucinogenic drugs, even though Haller in the novel uses them to achieve self-knowledge.

Sorrell, Walter, Hermann Hesse: The Man Who Sought and Found Himself, Owald Wolff, 1974, pp. 83-93.

This is a concise overview of Hesse's life and work. Most interesting for an understanding of Steppenwolf is the chapter on Hesse's ironic brand of humor.

Tusken, Lewis W., Understanding Hermann Hesse: The Man...