Dune. I wish I could read it the first time again twice. Once again like I did when I was a kid and took it at face value, being simply impressed by its depth and scope. Then once again like when I was older and realized that the book was really about the abuse of power, not just of the obvious villains but also of those whose seize power to defeat the villains but, in doing so, cause far more harm than the nominal villains ever did.