Another installment of absorbingly different, people-oriented sf from the USSR: three stories from each author plus the collaborative title novelette, all displaying a refreshing (and, in context, eminently reasonable) optimism. The title piece--a luminous, complex alien-contact yarn--concerns the meeting between explorer-technologist Shevtsov and the humanoid, translucent Sirians: they possess prodigious memories, vast intelligence, and musical genius . . . but they totally lack drive, ambition, or curiosity; and the encounter is eagerly monitored by a talented sculptor hoping to capture the elusive quality of space-age humanity. Altov's best: a comic gem (with serious import) starring compulsive, madcap inventor Antenna, whose electronic toys point the way to new machines capable of instant modification as technological breakthroughs occur; a set of space age fables, fascinating if scientifically reckless and mushy in spots. And Zhuravlyova, erudite as Lem but far less didactic, presents three fine tales featuring psychologist-extraordinary Kira, whose experiments in the self-discovered field of ""ultra-imagination"" lead to startling discoveries and prospects. (Unusually for Soviet export sf, too, politics rates several mentions: visionary Altov evinces a rather touching faith in the potentialities of communism . . . in intriguing contrast to iconoclastic Zhuravlyova, whose characters grouse about their salaries, aspire to owning automobiles, and remain ever-skeptical.) Thoughtful, provocative work--particularly on the distaff side--delivered with admirable warmth and wit.