Two of the scariest books I've ever read are Colman McCarthy's The Road and Thomas L. Friedman's Hot, Flat, and Crowded.
The Road, which has been made into a movie starring Viggo Mortensen and forthcoming in October, is the story of a man and his son wandering in post-apocalyptic America.
Just what's happened--nuclear war? environmental disaster?--isn't clear. But all of society's institutions have collapsed and the unnamed protagonist and his son roam through a bleak, unforgiving landscape where nothing grows and people eat other people to survive.
Hot, Flat, and Crowded shows us how this terrible future could come to pass.
It's a big book--438 pages--and Friedman would have been better served by an editor who made him cut 100 pages or so. Midway through, there's a a long, italicized section about how technology could help us use less energy without significantly altering the way we live that seemed more authorial self-indulgent than absolutely necessary to me.
But, quibbles aside, this is an important--and very scary--book that lays out in exhaustive detail how we got to the point where global warming threatens all life on Earth and what we can do about it.
Yes, Friedman says, there is a solution. The problem is, we needed to have started yesterday.