Definate classic. Good reading and feeds your imagination.
This is excellent classic sci-fi. It is the story of astronauts in the not too distant future rendezvousing with a mysterious cylindrical "spacecraft" dubbed "Rama" that had entered our solar system. The astronauts investigate the craft, discover how to enter it, and ... I won't spoil the rest. You'll have to read it yourself to find out what happens. Good stuff!
I love Arther C. Clarke. This is the starting point for the RAMA books he wrote with Gentry Lee. A good space mystery with a lot of "heady" sci-fi notions about alien encounters. Not a bad first book recommendation for someone who has never read Clarke's stuff.
Arthur C. Clarke is always a winner.