This post spoils Greg Egan's Incandescence.
Incandescence is a success story about some people who notice an existential threat and avoid it using science and engineering. We see them figure out how gravity works, which is more interesting than it might sound, partly because their everyday experiences are full of gravitational effects that we don't notice on Earth. At first they do science out of pure curiosity, but it turns into an urgent collective action problem when they discover that their orbit will lead them towards all sorts of disasters, including falling into a black hole. The solution, it turns out, is to move some dirt around.
Has anyone considered writing a success story about using Friendly AI to solve an existential threat?