After a lifetime’s worth of literature from Philip K. Dick that explored the future, the farthest regions of space and the afterlife, a posthumous work will take readers to a different alien terrain: the inside of the author’s mind.

Mr. Dick, who died in 1982 at 53, was best known for existential science-fiction novels like “The Man in the High Castle,” “The Three Stigmata of Palmer Eldritch” and “Do Androids Dream of Electric Sheep?” He also spent years wrestling with what he considered to be religious visions, which he began experiencing in the 1970s. He recorded his reactions to and attempts at deciphering these spiritual visions in a work he called the “Exegesis,” reputed to be 8,000 pages — or longer.

Though few have read the work and fewer still have fully understood it, the publisher Houghton Mifflin Harcourt plans to release “The Exegesis of Philip K. Dick” in two consolidated volumes edited by Jonathan Lethem and Pamela Jackson, a Philip K. Dick scholar, with the first to be released next year.

Mr. Lethem, the author of novels like “Chronic City” and “The Fortress of Solitude,” and who has written frequently on Mr. Dick, said Thursday in a telephone interview that he hesitated to describe the original, unedited “Exegesis” as a work.