Click for my thoughts on the first two books: Ender's Game and Speaker for the Dead.
I really enjoyed the first book in this set and really liked the second. The third, however, became a little bit much. Xenocide is much longer than they were and I found it even more dense than Speaker for the Dead. If I'm honest, I'm a little disappointed that I didn't like it the way I liked the first two books. But let me explain why.
It was dense. Wonderfully so at times--I still found lines that I could have underlined, concepts that were well-worded, conversations and ponderings about ethics and life. Nothing is, at its center, simple; yet everything is so complex that, in the end, it is rather simple. Much more philosophical questions are in this book and also much more of a sci-fi feel--at least I thought so. The first books were about anti-gravity, space, and aliens, but this book included the long-winded descriptions of such things as philotes and computer communication and viruses and interplanetary travel. Not that any of this is bad; I certainly don't mean to say that.
I'm just pointing out that, after enjoying my foray into sci-fi for the first two books, I'm getting a little bogged down by the setting now. This is more the type of thing I would have expected, in some ways. So now that I've finally gotten through its pages, I think I'll give it a longer wait before I read the last book in this set (not the entire series, I know). You can tell how I felt about this book from the fact that I have so little to say on it: neither much praise nor much criticism. Maybe I'll finally get to the new Tolkien poem and some others that have been lying in wait. There is always much to read.