I recently revisited Ender's Game via these graphic novels. They were a pretty good rendition of the book (at this remove; it's been years since I read the novel).
I was impressed with how quickly I became invested in the characters. I can't evaluate how that would work if I hadn't read the novels, though. I note that my 13-year-old son, while enjoying them, did not seem particularly excited about them. Hard to say, though -- he's less and less willing to SHOW excitement. :)
In any case, I thought these were well worth a read.