The good SF concentrate

I had excellent memories of this novel, which was an imposed reading when I was in fifth grade ... there are more than fifteen years now.
I have not been disappointed proofreading: fast action, concise descriptions but enough to give life to the distant planet Ygam and a basic idea that is taking the perspective on the evolution of the humanity, all this gives a concentrate of good science fiction. I recommend regulars such as beginners who want to rub it.