The book is an autobiographical memoir of Bukowski's years working at the United States Postal Service.

[1] An autobiographical account of Bukowski's years working as a carrier and sorter for the United States Postal Service,[2] the novel is "dedicated to nobody".

[2][3] The great love of Bukowski's life, Jane Cooney Baker ("Betty" in Post Office), was a widowed alcoholic, 11 years his senior, with an immense beer belly.

Bukowski's first wife, Barbara Frye ("Joyce"), suffered a physical deformity – two vertebrae were missing from her neck, giving the impression that "she was permanently hunching her shoulders".

In December 1969, John Martin founded Black Sparrow Press in order to publish Bukowski's writing, offering him $100 per month for life on the condition that Bukowski would quit working for the post office and write full-time for Black Sparrow.