Enders Game is good, so are the sequels.
The sequels (in the Ender Quintet) are good, but they are more philosophical than Ender’s Game. The Shadow Quintet books (that follow Bean) are more like the novel Ender’s Game.
I found Xenocide (the third book that follows Ender) to be hard to get into at times because the sections with Qing-jao were boring to me. The parts with Ender were much more interesting.