Twelve Anderson tales (eleven stories and the short novel ""The Man Who Counts""), presented as documents gathered for the benefit of Mankind's sometime friends and allies the Ythrians. The idea is not a happy one. But the lordly winged Ythrians have fascinated Anderson for years, and at this point enough material exists to flesh out a loose history of his Polesotechnic League, the powerful merchant consortium that supposedly dominated space traffic during the heyday of human-Ythrian cooperation. (Novels in the PL series include Trader to the Stars, Satan's World, and Mirkheim). These selections--some of them very arbitrarily dragged into the sequence--are typical lesser Anderson: conscientious establishment of scientific premises, sound plotting, vapid characterizations (especially of women), peculiarly hollow and toneless writing. Among the best are ""A Little Knowledge"" (apparently guileless alien outwits three freebooters), ""Day of Burning"" (the familiar Muddlin' Through crew prepare a squabble-ridden world against a coming supernova), and ""Esau"" (PL rookie breaks alien stranglehold on important cash crop). There are also some good glimpses of the fat, canny, irrepressible merchant Nicholas van Rijn, one of Anderson's more felicitous inventions. Okay for Anderson fans, otherwise a pretty corny project.