Once more, you can now download Arthur C. Clarke's classic, Rendezvous With Rama, for only 1.99$ here.
Here's the blurb:
An enormous cylindrical object appears in Earth's solar system, hurtling toward the sun. A ship is sent to explore the mysterious craft-which the denizens of the solar system name Rama-and what they find is intriguing evidence of a civilization far more advanced than ours. They find an interior stretching over 50 kilometers; a forbidding cylindrical sea; mysterious and inaccessible buildings; and strange machine-animal hybrids, or "biots," that inhabit the ship. But what they don't find is an alien presence. So who-and where-are the Ramans? Often listed as one of Clarke's finest novels, Rendezvous With Rama has won both the Hugo and the Nebula Awards. A fast-paced and compelling story of an enigmatic encounter with alien technology, Rendezvous With Rama offers both answers and unsolved mysteries that continue to fascinate readers decades after its first publication.