THE SIRIAN EXPERIMENTS by Doris Lessing Knopf; 288 pages; $11.95
This is the third installment of a space saga that Author Doris Lessing calls Canopus in Argos: Archives. That running title is matched by the pace of Lessing's production: three good-sized novels in the past 16 months. Shikasta (1979) tells of a primitive, beautiful planet called Rohanda, which is being jointly colonized by the two vast galactic empires of Canopus and Sirius. A misalignment of cosmic forces throws Rohanda awry; its developing inhabitants stop listening to their wise tutors and begin behaving suspiciously like...