Of the Ender series books, I've read the whole quintet - Ender's Game, Speaker for the Dead, Xenocide, Children of the Mind, Ender in Exile. I've enjoyed all five of them, although the quality drops which each of the instance. Speaker for the Dead is worth the time for sure, the other three I'm not entirely convinced. Speaker won a Hugo award in 1987.

Of Card's novels, the Shadow Saga, is a pretty good read thou. I've enjoyed it more than the Ender's one. It is set in the same universe, and focuses on Bean - another child from the Battle School. It drifts towards political fiction.