Barefoot in the Head (1972) by Brian W Aldiss

A new savior emerges from a drugged-out dystopia in "the most ambitious psychedelic sci-fi novel of the era" from the Science Fiction Grand Master (Conceptual Fiction).

The earth is recovering from the Acid Head War, in which hallucinogenic chemicals were the primary weapon. Many humans are now suffering from delusions and are unable to tell the real from the imaginary. When a man named Colin Charteris tries to make sense of the drugged-out world, he is taken as the new messiah. As he descends into paranoid visions, he begins to believe this himself.

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