In no particular order
Bryer, Jackson R. and Hartig, Mary C., eds. Conversations with August Wilson. Interviews and conversations that provide enlightening background on the plays.
Campbell, Mary Schmidt. An American Odyssey: The Life and Work of Romare Bearden. Bearden’s collages inspired at least two plays in the cycle.Wilson often cites Bearden’s influence.
Jones, Leroi. Blues People. One of Wilson’s major influences, along with Bearden, Borges, and the Blues itself.
Wilkerson, Isabel. The Warmth of Other Suns: The Epic Story of America’s Great Migration. Places the migration to Pittsburgh and to the Hill District in historical context.
Whitaker, Mark. The Untold Story of Smoketown: The Other Great Black Renaissance. Everything you ever wanted to know about Pittsburgh. Lots of context for the plays in the cycle.
Muhammad, Elijah. Message to the Blackman in America. Wilson credits Muhammad with supplying the first mythology (origin myths) for black Americans.
Temple, Riley. Aunt Ester’s Children Redeemed. Short critical analyses of each play in chronological order. Recommended for the course but not required.
Bigsby, Christopher, ed. The Cambridge Companion to August Wilson. Essays on each play and on recurrent themes. All the top Wilson scholars are represented.
Shannon, Sandra. The Dramatic Vision of August Wilson. Extensive essays on the first six plays in the order written, plus an unabridged interview with August Wilson makes this volume a plus! I reference this volume often in discussions.
Snodgrass, Mary Ellen. August Wilson: A Literary Companion. A dictionary-type listing of all the characters and themes of the first nine plays (published prior to the completion of Radio Golf) along with a multi-generational timeline of all the events in the plays. Very helpful.