A good SF novel of the fifties part of the trilogy of the Galactic Empire (3 independent both novels the characters, the places of their time, and the only common point of which is to describe different stages of development the Galactic Empire "Pebbles in the sky", "The currents of the Espace" and "Tyrann (or stardust)"). This trilogy is the link between the cycle and the cycle of robots Foundation. "Pebbles in the sky" develops a good story well chiselled with subjects always news revolving around racism, prejudice and tolerance. Here is the Galactic Empire who shows contempt and dostracisme towards land causing some of them to become radicalized and try to destroy the Empire. As usual with Asimov, the plot does not lack finesse or consistency. In addition, the "good doctor" makes good use of future developments in science (although the "technological" side Asimov does indeed deepens never in his novels, a little dated, what matters in Asimov these are the major scientific developments, not "gadgets"). The only minor (common among Asimov) psychological development is not enough depth of the characters.
