The Ballad of the Sad Cafe explores themes which include gender roles, love, loneliness and isolation. These emotions and themes reflect events in the author's life. That is, the book has autobiographical themes and that is why the book was written (at the time it was written).
In 1937 McCuller married James Reeves, but their marriage was never very stable. The pair separated in 1940, divorced in 1941, temporarily reconciled later that year, and then remarried in 1945.
During their period of temporary reconciliation in the Spring of 1941, the pair grew enamoured of the composer David Diamond. The ensuing 'love-triangle' is depicted in The Ballad of the Sad Cafe. This love-triangle eventually led to the re-estrangement of Reeves and McCullers
Her own health concerns, and living in an artists' residence in Brooklyn Heights, provided other experiences to drawn on for her writing.
Earlier works, especially Reflections in a Golden Eye had also explored themes personal to the author - impotency, bisexuality and infidelity.