The basic plot of The Fountains of Paradise can be summed up with two words: space elevator. Yes, it's something of an architectural procedural, and much of the story is taken up with the events of the project lead (Vannevar Morgan) to get the thing started. Luckily, this is also terribly interesting, far more so than I ever would have guessed. Morgan wants to build his elevator on the fictional island of Sri Kanda (essentially Sri Lanka moved to the equator), but there's the small problem of an ancient monastary in his way.
I did take a little issue with how easy Clarke made the construction look. It's all dully smooth sailing, save for one incident near the end. Because while Clarke at least addresses most of the issues facing space elevators, he tends to gloss over them very quickly, and there's little trial and error or mishap involved. The cast is also almost impossibly small, with only four or five people appearing in more than one scene.
There's also an odd bit with a robotic probe from another intelligent civilization. This probe is intelligent enough to completely refute Aquinas, which somehow leads to the vast majority of the world's population completely abandoning all religions. And this is, essentially, a side note that didn't seem to serve any purpose to me. Aside from the believability factor, it's inessential to the storyline and actually serves as a distraction.
All that said, The Fountains of Paradise is, for the most part, engaging to listen to, and the few characters are mostly interesting people. The concept of a space elevator is fascinating to me, and the science is pretty close to hard, and makes it look like both an appealing and a potentially near project.