I think this may be the first science fiction work I ever read. My dad had one of those Sci Fi Book Club editions with all three novels in one volume. I might have been in 6th grade the first time I read it, although I came back to it again and again. This is the book that made me a science fiction reader, I was so captivated by the richness of the universe Asimov created and the epic scope of the story. My favorite part remains the section about The Mule.