Shadow of the Hegemon by Orson Scott Card
Published January 1, 2001
So you've just finished reading Ender's Shadow. Ender Wiggin, having defeated the Buggers--er, Formics--once and for all, has left our solar system with his sister Valentine for the first extrasolar colony. Their older brother, Peter, is still hiding his identity on the nets behind the personas of Locke and Demosthenes as he manipulates global politics. Ender's generals, including the superintelligent Bean, a.k.a. Julian Delphiki, have all gone back to their native countries to try and resume life as best they can.
Oh, and Russia has just tried and failed to take over the global government established to fight the Formics. They want to try again. Toward that end, they kidnap Bean's adversary, a brilliant and charismatic boy known as Achilles who just barely qualifies as a student of the Battle School. See, Achilles was thrown out of Battle School when Bean tricked him into confessing to seven premeditated murders. He's not too valuable as a military general, but he's very, very good at thinking three or four moves ahead of his benefactors.
And so it is that, about a year after all the Battle School children have returned to Earth, ten of the students who commanded fleets directly under Ender are kidnapped within hours of each other, and Bean's family's vacation home is destroyed. Fortunately, Bean is smart enough to get his family out of the house before it happened and identify the kidnappers as Russians working for Achilles. There's only so much he can do for now, though, since (a) Achilles will certainly try to kill him again and (b) he has no idea exactly where in Russia his friends are.
By the time he locates them, they've already been evacuated, with only Petra Arkanian--an Armenian and one of the few girls ever to enter Battle School--traveling with her captor to India, Pakistan, and China as Achilles makes allies in every major Asian country and sets in motion World War III.
Unlike Card's previous novels in the Enderverse, the "Shadow" novels are less about science fiction than international politics and military action. This trilogy (or quartet, if you include Ender's Shadow) centers around both Bean and Peter Wiggin, the future Hegemon of all the earth but who for now is still a teenager living at home with his parents. Peter has to somehow stop every major national government from pursuing their opportunistic conquests and get them to agree, one by one, to stop fighting each other and form a single world government. Only a unified, peaceful government can colonize space and ensure that humanity is too widespread to ever be wiped out as the Formics (allegedly) were.
That's the greater story. The smaller story is, of course, about Bean, who does not yet know the whole truth about how he was genetically engineered for nearly unlimited intelligence in exchange for an early death. Bean has just discovered his family, as well as his emotional bond to Petra, and he'll do anything to keep Achilles from taking them all away from him. Stopping World War III is something of an afterthought.
Needless to say, Bean, Petra and Peter all have somewhat different ideas as to how this all ought to be done. As if being a teenager wasn't hard enough....
This book is preceded by Ender's Shadow and followed by Shadow Puppets and Shadow of the Giant.