This book is set in a not-too-distant future where humanity has settled several of the planets of the Solar system. A gigantic celestial body, weighing several trillion tons, is observed to be entering the system. The body is moving at an incredible speed, and is initially christened “Rama”. As the body grows closer, a space probe notes that it is not a natural object. In fact, it is perfectly cylindrical.
The planets hurriedly put together a mission to land on the object and possibly, for the first time in human history, make contact with an alien civilization.
The ship lands on the flat surface on the leading edge of the cylinder, and passes through a triple airlock to enter the confines of the cylinder. Inside they find an entire macrocosm, and an atmosphere close enough to Earth that they don’t need breathing apparatuses. They set about exploring the world on the inside of the cylinder and possibly meeting and communicating with the aliens in the limited time they have, before Rama slingshots around the sun and exits the Solar system.
Their adventures inside Rama, and their ingenuity in exploring the depths of the body, and also preventing hostile planets in the System from taking drastic actions form the bulk of the narrative.
This is a plot-driven story, rather than the more conventional character driven stories that form the bulk of literary works nowadays. They story focuses on the the teams’ efforts on understanding the mechanics and environment of the alien world, and their ingenuity and thought processes as they come up with novel ways to efficiently explore Rama.
Their wonderment at the fantastic sights they see, and their speculation about the nature and purpose of everything they discover is a pleasure to read. In an era where man has conquered and settled his entire system, being pioneers is in itself unusual.
In the end, they run out of time, and have to leave in their ship as Rama starts its acceleration towards the sun in anticipation of the slingshot. The nature of Rama, as well as the identity of it’s creator remain an enigmatic mystery, and the crew are left with the realization that Rama was neither benevolent nor malevolent. It has a greater purpose where humans and their antics are inconsequential; And that purpose would remain a mystery to humans.