Dune
If we use readership to evaluate the best science fiction book for young adults, then the honor would surely go to Frank Herbert's Dune.
In Herbert’s universe, computers, robots and other artificial intelligences are outlawed. In their place, civilization has developed advanced mental and physical abilities as well as advanced technologies that comply with the edict on computers. Dune tells the story of House Atreides, specifically Paul Atreides, whose family accepts the stewardship of the planet Arrakis.
Arrakis is an inhospitable desert wasteland (with more than a few surprises!) and it is the only source of melange in the universe, a drug that provides multidimensional awareness and foresight to space pilots.
Control of the planet is a profitable but dangerous undertaking. The story explores the politics, religion, ecology, technology, and human emotion, of the different noble houses as they struggle for control of Arrakis and the melange.
