Miss MacIntosh, My Darling (Volume 1)

Blurb

Miss MacIntosh, My Darling is a novel by Marguerite Young. She has described it as "an exploration of the illusions, hallucinations, errors of judgment in individual lives, the central scene of the novel being an opium addict's paradise."
The novel is 11th on the Wikipedia List of longest novels, and 5th among novels written in English.