Sorry, but Rendezvous with Rama is boring as hell. How can anyone turn exploring an alien spaceship into a dry-as-dust textbook? I can summarise it for everyone: they go to an alien spaceship, nothing happens, and you learn nothing interesting about the people involved. Now you don't need to waste time reading it yourselves. Oh, and Clarke bolted on a dreadful final few paragraphs to explain away the pointlessness of it as the first step in a series, although it's on record that he never actually intended to write any more Rama books.
As for the rest of the series, I got the first two sequels together, thinking maybe having a collaborator would improve things. I was sort of tempted to get the final one just to see how it turned out. But I decided that since I didn't care about any of the characters, and the writing was almost physically painful in the awfulness of plot, characterisation and dialogue, on principle I wasn't throwing any more money their direction. Gardens of Rama in particular is in my personal hall of infamy of books without a single redeeming feature.