First off, the sci-fi element is grand. Wonderful detail concerning mechanical and biological systems, as well as logistical solutions. Well written and easy to read and understand.
Second, OSC had to write genius interior and exterior dialogue - some from adolescent POVs. That could be difficult to pull off, but I bought it. Some of the quips were funny.
I'll stop counting now -- reading sci-fi stimulates my left brain. I have read most of the Ender series, so this installment made sense and added an interesting and creative perspective. There were a couple of explorations into the nature of language and mind -control that I loved. Adventure and space stories can be fun, but I'll give an extra cheer for those that teach me something or are thought-provoking.
My criticism with the novel is that despite all the positive qualities, it still felt shallow and sketchy. For basic story-telling qualities alone, such as character development, etc, I'd give it 3 stars. For example, the story starts with Ender, one of the genius children, then hops to the other two children, so we get to know them, which is fine. However, the real owner of the story is Bean. Once the baton is passed to him, it becomes more interesting because he has the history and maturity. Artistically, (right brain - is that you?) I think the entire framework should have been from Bean. But then, who am I to criticize Sir Card? I can say, I liked the earlier Ender novels better because they had more meat in the present story, rather than in the back-story.
Conclusion? If you liked the Ender series, you'll appreciate this installment, but don't start here.