Orson Scott Card wrote two separate series that begin with the International Fleet's preparation for the Third Invasion of the Formic War. The Ender Series follows Andrew Wiggin's life, while the Shadow Series follows Bean's (Julian Delphiki). Ender's Game is the first novel of the series based on Andrew Wiggin, commander of the human fleets, who destroys the buggers. It follows Ender's military training from agre six until the end of the war at age eleven, continuing while Ender joins the first colony on the new worlds. Ender's Shadow follows Bean's life on the streets of Rotterdam and then into Battle School. These two novels, the first books in each of their respective series, are considered parallel novels. Parallel novels are usually novels that cover the same period of time and the same plot from the perspective of different characters.
Bean is largely peripheral in Ender's Game, a latecomer who appears in the tenth chapter. While Ender notices Bean's brilliance and talent, Bean is a bit too young to be real competition for Ender. He takes a teacher's perspective toward Bean, such as when he isolates Bean much like Graff and the other teachers isolated Ender when he first arrived at Battle School. By the end of the novel, Bean has become one of Ender's closest friends, but he falls out of the novel after the war. In fact, Ender specifically states that while Bean is "like a scalpel" with a small number of ships, Bean may not be able to control a large number of fighters, unlike Alai or Petra.
But Ender's Shadow creates a new dimension of Bean's involvement in Ender's life. We find out that Bean has been studying Ender for quite some time by the time he is assigned to Dragon Army, even though he never joined in Ender's launchie practices. Bean also broke into the teachers' computer system and studied and evaluated all of the students in Battle School. We realize, in Ender's Shadow, that Bean has actually designed Dragon Army for Ender. Ender thinks, in Ender's Game, that when his group of inexperienced launchies and unknown veterans is put together, the adults have stacked the deck against him and that he will have to work hard to form a talented and well-coordinated army. But Bean created it to be that way.
We also learn in Ender's Shadow that Bean is the one chosen to be Ender's replacement if something happens to Ender. The teachers and officers of the International Fleet discuss whether Ender or Bean would be the better commander against the Formics. It is ironic, therefore, that Ender considers Bean to be the least able to control large numbers of ships; when Mazer asks Ender who would be able to take over from him, should Ender fail, Ender replies that it is Alai, not Bean.
Finally, Ender's Shadow has a very different ending than its parallel novel, because Bean, the most brilliant of the Battle School children, does realize that all of their "games" against Mazer are real battles against the buggers. When Ender commands his ships to attack the planet in the final battle, Bean realizes that this is complete suicide, and he says a prayer over the ansible to the men who are sure to die in the attack. No one else realizes that these battles are real, and thus Bean is the one to tell all of the other squadron leaders that the war is over. Bean's intellectual skills help him realize many things that no one else does.
The rest of the novels of the two series are not parallel novels. The Ender series is completed with Speaker for the Dead, Children of the Mind, and Xenocide, which all follow Ender's exploration of other worlds. The Shadow series, on the other hand, continues with Shadow Puppets, Shadow of the Giant, and Shadow of the Hegemon, which follow Bean's influence on Earth and its wars. The Shadow series also includes a focus on the other squadron leaders from the Bugger War as well as Peter Wiggin, while the Ender Series continues to follow Valentine's journey with her brother. These differences and comparisons yield additional insight into Card's own interpretation of the significant characters and events of Ender's Game.