Kavin's World

Classic sword and sorcery novel by David Mason.
Most of his novels - such as his first, Kavin's World (1969), and its sequel in the Kavin sequence, The Return of Kavin (1972) - were routine Sword and Sorcery. However, his final book, The Deep Gods (1973), more impressively implants a twentieth-century mentality into the brain of a prehistoric man (see Identity Transfer), where he must deal with the insanity of a whale (one of the "deep gods" of the title) that threatens to destroy Eden." -Science Fiction Encyclopedia