Arthur C. Clarke & Gentry Lee 
Rama: The Omnibus 
The Complete Rama Omnibus

At first, only a few things are known about the celestial object that has arrived in the galaxy and has been dubbed Rama by the astronomers observing it. It is a huge cylindrical object, weighing more than ten trillion tons. And it is hurtling through the solar system at inconceivable speed. Then a space probe confirms the unthinkable: Rama is no natural object. It is, incredibly, an interstellar spacecraft.Space explorers and planet-bound scientists alike prepare for mankind’s first encounter with alien intelligence. It will kindle their wildest dreams … and fan their darkest fears. For no one knows who the Ramans are or why they have come. And now the moment of rendezvous awaits — just behind a Raman airlock door.