If science fiction themes can be distinguished as "science fiction as character" (Star Trek), "science fiction as background" (Star Wars), "science fiction as trigger" (ET), "science fiction as story" (The Matrix), then The Breeds of Man definitely falls into the "science fiction as story" theme. It falls squarely between hard and soft sci-fi. The science isn't as plausible as say, "Deep Impact," but far more believable than say "Starship Troopers." The story plunges you into a world where the AIDS virus still plagues us, but has started mutating rapidly. When an airborne variation surfaces, scientists kick it into overdrive to find a vaccine or a cure. The resulting solution triggers another problem that scientists must solve. And this ultimate solution results in the breeds of man. It is difficult to fully review the book without giving away spoilers, but the pacing was good, if you are not in the virology or immunology fields, then the science was plausible enough not to be irritating or distracting and the tension and suspense kept you reading. It is a fun quick read, a bubble gum for the eyes, and just as enjoyable.