I just finished A Deepness in the Sky by Vernor Vinge, and it was the most enjoyable book I have read in the last couple years. I’m not going to spoil the plot, but like all Vernor Vinge books it has layers upon layers with themes such as civilizations rising and falling, technological progress (and sometimes regression) with its opportunities and dangers, interactions between civilizations at different levels of technology, and at similar levels of technology but with different cultures and values. The plot unfolds over long periods of time while the characters are very real, accessible, and human, even if not all of them are actually human.