Science fiction is often divided into two main genres: soft and hard. Soft science fiction tends to be more humanistic, with a greater emphasis on traditional story and character development. Ursula Le Guin, Theodore Sturgeon, and Cordwainer Smith are good examples.
Hard science fiction tends to focus on concepts, with more weight given to scientific rigor and speculation. Its lineage stretches from Asimov and Clarke to modern authors like Greg Bear and Alastair Reynolds. It's not to say these guys can't write stories, but this is primarily a literature of ideas.
That's where Watts comes in. His books are defined by pessimism towards the future and a density of scientific detail. He wants to make a point as well as tell a story.