Of course, once you read Ender's Game (Rating: 5 out of 5)you must read the rest of the series!
Then, there's Ender's Shadow (Rating: 5 out of 5), which I might argue is actually better than Ender's Game. Ender's Shadow is the companion novel to Ender's Game, except instead of following Ender, it follows Bean, the youngest and smallest, yet brightest, of all the children at Battle School. He acts as Ender's right-hand man when Ender is commander; Ender must depend on Bean to get the job done. But, of course after the Buggers are defeated, it's not over yet for Bean. In Shadow of the Hegemon (Rating: 4.5 out of 5), each of Ender Wiggin's army are kidnapped. After the success with the Buggers, the brief moments of International Peace are gone, and replaced by the desire to gain more power. Shadow Puppets is a fantastic read as well. (Rating: 5 out of 5)
Card writes in a very unique way; he pops into action, leaves suspense hanging, and makes you want to read the entire series in one day straight. Comedy, romance, action, adventure, suspense, drama -- it's got all of them combined!