Last year NPR put out a list of the top 100 science fiction and fantasy novels as voted on by their listeners. Such lists can be helpful for keeping up with the current zeitgeist of a genre (or in their case, genres). However, lists voted on by the public tend to severely underestimate the influence of older works which are not currently on everyone’s mind. For a more balanced picture of a genre, you need to find a list like the one created by the Center for the Study of Science Fiction at the University of Kansas. They created their Basic Science Fiction Library to help public libraries know what books they should carry and to help scholars understand which authors have been influential in shaping science fiction over time. Many of these books are older; not all of them are either in print or available for the Kindle. However, the majority can be found.