One could probably write a book on all the things that influenced Star Wars, maybe even two or three. The franchise was always built on the Hero's Journey, a model coined by Joseph Conrad that was itself based on thousands of years of literary tradition. We can see plenty of influences from classical Hollywood, particularly westerns and old WWII movies. There are elements of Japanese Samurai films, especially those of Akira Kurosawa. We can also see traces of old serials and earlier science fiction. There is a bit of Flash Gordon and Star Trek. There are even pieces of actual history thrown in, such as the way the Empire is not-so-subtly based on the Nazi regime, to the point where their soldiers became known as "stormtroopers." But one particular source of inspiration stands out. There is one iconic sci-fi book that was clearly a massive influence on Star Wars.