You can now download Arthur C. Clarke's classic, 2001: A Space Odyssey, for only 1.99$ here.
Here's the blurb:
The year is 2001, and cosmonauts uncover a mysterious monolith that has been buried on the Moon for at least three million years. To their astonishment, the monolith releases an equally mysterious pulse—a kind of signal—in the direction of Saturn after it is unearthed. Whether alarm or communication, the human race must know what the signal is—and who it was intended for. The Discovery and its crew, assisted by the highly advanced HAL 9000 computer system, sets out to investigate. But as the crew draws closer to their rendezvous with a mysterious and ancient alien civilization, they realize that the greatest dangers they face come from within the spacecraft itself. HAL proves a dangerous traveling companion, and the crew must outwit him to survive. This novel version of the famous Stanley Kubrick film 2001: A Space Odyssey was written by Clarke in conjunction with the movie’s production. It is meant to stand as a companion piece, and it offers a complementary narrative that’s loaded with compelling science fiction ideas.