The man who, a quarter of a century ago in The Chariots of the Gods, introduced the concept of "ancient astronauts" to an eager public now attempts to codify his more recent findings into a coherent theory. Von Dniken calls this theory PALAEO-SETI-PHILOSOPHY, where SETI stands for the Search for Extraterrestrial Intelligence. The theory's twin foundations are von Dniken's literalistic readings of ancient religious texts and, ironically, his hidebound materialism. He assumes that texts such as the Bible, the Mahabarata and others are true accounts in nearly every detail, and also that science has proven that gods or supernatural beings don't exist. The inference, then, is that all the miraculous goings on in these writings and oral poems were the work of aliens so advanced that they looked magical or divine to ancient peoples. Von Dniken's evidence comes from his single-minded and self-serving readings of the texts, in which it seems as if every flaming chariot must be an alien shuttlecraft, every creature with monstrous attributes must be an alien-human hybrid and every messiah or angel is an extraterrestrial overlord dictating human affairs from a space station in Earth orbit. The argument culminates with the claim that the aliens' message to humanity is not encoded in the pyramids or other physical structures but in human genetic structureDhence the current phenomenon of alien abduction, in which intrusive tests are performed on abductees. As in his earlier books, here von Dniken manages to be nearly as entertaining as he is preposterous to those who don't already believe. His prose is lucid, his argument is more or less coherent and the whole idea, whether one buys it or not, is still engagingly daffy. (Feb.)