Is this ""the great American novelization"" (said the New Yorker wife to her hard-typing spouse)? Spielberg, the director of Jaws, has novelized his own filmscript for his science-fantasy Close Encounters of the Third Kind, which goes into release Christmas week. And for most of the way he manages to titillate the reader toward the book's big all-stops-pulled superfireworks finale. The subject is ""the most important moment in the history of the world"": contact with visitors from outer space. Not just visitors, but a whole skydarkening city of visitors, which is touching down in Wyoming. Harbingers of the tremendous event are everywhere, with a madness of flying saucers over Indiana, weird electrical phenomena, power blackouts and--the return of that Navy flight squadron lost in the Devil's Triangle back in '45, with its pilots still the same age! The story's big middle scene, a chiller where all the electrical appliances in a house go crazy, with a vacuum cleaner chasing the heroine, seems out of tone with the ""religious"" jubilation of the climax--but few will care. Nor are Spielberg's strategies as a novelist equal to the stunning visuals of the glorious finale he roughs in. Perhaps the book's main flaw is that it exposes the two-dimensional characters that the film may flesh out. Otherwise--great entertainment.