Willy Ley (sometimes credited as Willie Ley) was a German-American science writer and space advocate who helped popularize rocketry and spaceflight in both Germany and the United States. The crater Ley on the far side of the Moon is named in his honor.
Excellent introduction to the history of astronomy and cosmology. A bit dated now. Good substitution is Coming of age in the Milky Way by Timothy Ferris.