I am a retired sailor. The Ender Quartet should be required reading for all military leaders: nomcoms and officers. Author Card captures the essence of leadership: trust, confidence, and commitment in "Ender's Game"; and the personal consequences of war, the fragility of racial tolerance and compassion, and the ghosts that haunt veterans (many for the balance of their lives) in "Speaker for the Dead", "Xenocide". and "Children of the Mind".
I read each of the eight books that today comprise the Ender's Quartet and the Ender Shadow series, book by book, as they were first published, in the last quarter of the 1900's; many of them in my bunk, braced against rolling seas.
Spurred by Card's most recent "Ender in Exile"--a gift from a friend--I purchased both the Quartet, and the Shadow series, and read each anew, certainly, with different eyes than the first reading. I suggest that Orson Scott Card has taken a seat along side Asimov, Hienlien, and Clark. Be you veteran, neophyte, pacifist, activist, monk, clergy, healer, historian, leader, follower, or dreamer of better worlds there is something in the Quartet for all of us.