A rather one-dimensional but mostly satisfying child-soldier yarn which substantially extends and embellishes one of Card's better short stories (Unaccompanied Sonata and Other Stories, 1980). Following a barely-defeated invasion attempt by the insect-like alien "buggers," a desperate Earth command resorts to genetic experimentation in order to produce a tactical genius capable of defeating the buggers in round two. (A counterinvasion has already been launched, but will take years to reach the buggers' home planet.) So likable but determined "Ender" Wiggins, age six, becomes Earth's last hope--when his equally talented elder siblings Peter (too vicious and vindictive) and Valentine (too gentle and sympathetic) prove unsuitable. And, in a dramatic, brutally convincing series of war games and computer-fantasies, Ender is forced to realize his military genius, to rely on nothing and no-one but himself. . . and to disregard all rules in order to win. There are some minor, distracting side issues here: wrangles among Ender's adult trainers; an irrelevant subplot involving Peter's attempt to take over Earth. And there'll be no suspense for those familiar with the short story. Still, the long passages focusing on Ender are nearly always enthralling--the details are handled with flair and assurance--and this is altogether a much more solid, mature, and persuasive effort than Card's previous full-length appearances.