Arthur C. Clarke is often credited as one of the “Big Three” fathers of modern science fiction along with Asimov and Heinlein, so it’s a bit surprising that it took him until the '70s to win a best novel Hugo. Rendezvous with Rama is a great first winner for him though. This is probably his best novel, and it's science fiction at its purest.
In the 22nd century, astronomers on Earth sight a large object moving through the solar system with some odd characteristics. A probe soon shows that the object is a perfect cylinder over 50 km long – obviously artificial, and thus the first alien ship that humanity has ever seen. A ship from Earth is redirected to rendezvous with the vessel, and the bulk of the novel consists of the exploration that follows. A crew of astronauts enter the ship, which is apparently uninhabited by sentient life, and explore it, while governments throughout the colonized solar system debate what to do with this new discovery. The exploration is particularly fun, as the astronauts use the odd characteristics of a cylindrical world that generates all of its gravity by centripetal force to do some interesting things.
I’m not going to get to into the specific mysteries or conflicts – suffice it to say that it’s the mood that matters. Rarely do you get a book that’s both thoughtful and exciting as this one. It’s a fairly simple story, and the characters can be a bit interchangeable, but Clarke really shines at portraying the wonder and mystery of a great discovery. The novel is absolutely thrilling. It’s definitely a page-turner. I highly recommend it, and it was very deserving in its sweep of the major sci-fi awards.
I will add that I’ve actually read the sequels. Unfortunately, the law of diminishing returns definitely applies with the Rama series, which were mostly written by Gentry Lee, not Clarke. Rama II recreates some of the mysteries and discoveries of the first novel, but the series soon focuses on the conflicts that emerge among the human explorers (and eventually settlers) of another Rama probe. There’s more exploration of social issues, which I usually enjoy, but there’s an overwhelming pessimism and misanthropy that really cuts into the original novel's sense of wonder.