After a digression into sexual politics (The Marriages Between Zones Three, Four, and Five), Lessing's science-fiction cycle returns to the broad sociological preoccupations of Shikasta (1979)--in which we learned of the Canopean Empire's benevolent, triumphant, yet doomed experiments with primates on Colonised Planet 5, Shikasta. Now the focus is on the very un-benevolent experiments carried out by the Canopeans' rival Empire-builders--the Sirians, who control Shikasta's southern hemisphere. And Lessing's Sirian narrator is Ambien II, a crisply efficient bureaucrat/scientist who will gradually come to realize that the Sirians' obsessive, envious fears of Canopus are unfounded, that the Canopean guiding-principle of "Necessity" is valid, that the Canopeans are "altogether finer and higher." But before this awakening, Ambien II masterminds some dreadful experiments: the kidnapping of thousands of "Lombis" from Planet 24 for training as slaves (kept in a social vacuum to prevent upward mobility, this easygoing race becomes nervous and paranoid); pathetic stabs at simulating the miraculous Canopean rapid-evolution experiments; doomed attempts to alleviate the existential malaise of Sirians ("enfeebled by soft living") via Shikastan work camps. And this experimental era ends only when the entire planet falls under the disastrous influence of planet Shammat, evil incarnate; Sirius gives up on Shikasta completely. Canopus never loses interest, however, and millenia later, altruistic Klorathy of Canopus guides Ambien II back to Shikasta, now dotted with assorted cross-bred civilizations: Utopian Adalantaland, which vanishes beneath the sea when Shikasta suddenly tilts on its axis; the decadent city of Koshi, where Ambien II engages in a good-vs.-evil duel and begins doubting all her Sirian principles; the theocratic slave-state of Grakconkranplatl, where she's taken prisoner; the lovely democracy of Lelanos, which (like all good things, apparently) is doomed to fall away into despair. (Ambien II herself temporarily descends into "Shammat-nature" and leads the spoiling of Lelanos.) And finally, after joining Klorathy in a scheme to avert total Shammat devastation on Shikasta's moon, Ambien II starts denouncing her own Sirian government (a dictatorship in disguise) and winds up "under planet arrest". . . As narrative, Ambien's report is largely unsatisfying--episodic, shapeless, choppy. As a crammed forum of ideas, it's sometimes provocative, more often murky, with distracting, conflicting signals along the way (e.g., Canopus seems to be part Marxism, part God, part Britain). Still, the notion of intellectual awakening--a delicate transformation sometimes illuminated here with dazzling sharpness--is strong enough to pull the whole, challenging, disorganized piece together. Demanding and uningratiating, then, but--like previous Canopus volumes--worth the effort of readers attuned to the very biggest questions.