Eleven ingenious tales, 1944-81, emphasizing alien thought and logic over the merely grotesque or horrid beloved of TV and the movies. First, there's a sterling set of famous oldies: Murray Leinster's ""First Contact,"" where humans meet potentially hostile aliens in space--so, to avoid a calamitous battle, they swap ships; Lawrence O'Donnell's ""The Children's Hour,"" an eerie love story where the girl turns out to be one single facet of a multidimensional superbeing; Katherine MacLean's ""Unhuman Sacrifice,"" about alien children who, on becoming adults, metamorphose into bushes; Paul Ash's ""Big Sword"" (tiny grasshopper-like aliens are prevented from reproducing sexually by a geological catastrophe); and Eric Frank Russell's ""Hobbyist,"" in which a godlike alien seeds empty planets with manufactured lifeforms. Also outstanding: Fredric Brown's waggish piece, written during the golden age of radio, describes the invasion of Earth by radio-wave beings; and Marc Stiegler's flawed but fascinating tale of aliens whose adult lifetimes last only 36 hours. On the debit side, there's a clunker from Poul Anderson (intelligent birds) and an out-of-place item from Eric Frank Russell (Earth spy outwits his game-playing alien captors). Otherwise: a satisfying, thought-provoking anthology, whose one possible drawback is over-familiarity.