I'll bet that if we took a poll, Ender's Game would be near the top of the list for a lot of Zoners.

'Fraid you'll have to count me out. I've read only two of them: Ender's Game itself and Speaker for the Dead, and it took me until 2005 to get to them. I haven't yet looked at the parallel Bean-centered series, even though Mary Anne recommended them. Yes, they were good -- in my internally-visual way of judging, meaning mostly that the author keeps me right there in the scene. But I didn't find them as compelling after the initial reading as many others have.

In fact, the most significant impression those books left on me was the side-story about Valentine and Peter, as they became political 'bloggers' -- written before the concept existed, let alone the word was coined -- with strong reference to essays written by Adams, Jefferson, Madison, Hamilton et al. in their day (my favorite historical period), under Latin or Greek pen names. I was reminded at the time of HZ, with Mary Anne as "Demosthenes".

Ender's Game has significance to me in another way, though. Even though it took me 20 years, I saw the first successful blending of a young-adult adventure (cf. Heinlein's Tunnel in the Sky) with a questioning of the motives and conduct of war (cf. Haldeman's The Forever War). It's an important message, and Card's book are a good way to deliver it.