They are all so good! Years ago a read Ender's Game and Ender's Shadow and I really enjoyed them, but I had no idea that they were a whole series. Mike figured it out and read all of them and really loved them, so I took the plunge and started reading them again.
Guys, Ender's Game is so freaking cool. I've read it twice and each time throughout the whole thing I think to myself, "this book is so cool". Then at the end I think, "this book is so freaking cool".
I highly recommend them. All three of the later ones are so different than the first one and not quite as exciting in my opinion but still really good.
There is another series that is about one of the characters and goes off in a sort of different direction. Ender's Shadow is basically the same story as Ender's Game but from someone else's point of view. Sounds like it could be lame to read the same story again even though you already know the ending but it is actually awesome.
I'm only on the second one in this series but I'm loving it already. If you're looking for some reads, I recommend these. Let me know what you think if you do!