A dated book, and definitely not Niven and Pournelle's best. Instead of global warming, the Earth is being covered by glaciers, thanks to those silly environmentalists and all their anti-pollution laws, which literally reversed the Greenhouse Effect. Two astronauts from the space habitats still orbiting the Earth are shot down over North America, and have to be rescued, by sci-fi fans. (Hah, see me use "sci-fi" deliberately just to annoy all the SF
pedantists?) Half ego-fluffing for SF fandom, half polemic against environmental laws and politicians who cut the budget for the space program, this novel read like ranty fan fiction, and the writing, honestly, was not much better. I gave it three stars mostly because of my lingering fondness for Niven and Pournelle and because I'm just geeky enough to have caught most of the in-jokes, but if you're going to read this, I highly recommend getting the free ebook from the Baen Free Library.