THIS PROMISED LAND

First in a projected trilogy about California's past, this high-minded but broken-gaited novel deals with pioneer explorations and colonizations in southern California's 18th-century ""New Spain."" And the primary emphasis is on cross-cultural romance--as Lospe, daughter of a Chumash chief (whose fictional domain lies somewhere between Malibu and Morro Bay), falls for Antonio Boneu, a Spanish aristocrat who favors Rousseau's vision of the ""natural"" society. Antonio starts out riding with the ""Sacred Expedition,"" led by General Gas-par Portolo, to extend the territory of New Spain. But on the long trek to reach the port of Monterey by land, Antonio and his black friend Pablo briefly leave the march and stumble for a while onto the Promised Land of Lospe's people--handsome, intelligent, seemingly living in peace. Lospe's family, however, is soon decimated by the cruelty of wily shaman Owataponus: her father is dead, her mother forced to wed the brutal shaman, and brother Asuskwa has fled. (Eventually Asuskwa will ritually kill the shaman and disappear, to rally other tribes in a doomed effort to drive out the white invaders of Indian land.) So, to escape the evil power of Owataponus, Lospe flees to the gentle priest at the nearby mission, converts, adopts the name ""Clara, and weds Antonio: they're given a land grant and have a son, Francisco. Yet their dream of Indians and Spanish living side by side in peace will never be realized. There will be atrocities on both sides; in the name of religion, Indians will be enslaved by a few unscrupulous priests; Indians will become demoralized and fail to unite; Francisco will be corrupted, hating his ""half-breed"" heritage; and there's that new breed of ""Americans""--with manifest destiny on their minds. Some clumps of drama, some abruptly anachronistic commentary (""The mountains closing in near the present site of the Hearst Castle forced them to stop"")--but chiefly of interest for the detailed backgrounds (real-people cameos, the Sacred Expedition, Chumash religion, cruel animal sports), which have all the pep so lacking in Easton's characters.