To misquote the Duke of Gloucester: "Another damned, thick, square book! Always scribble, scribble, scribble, eh, Mr Niven?" (And Dr Pournelle.) The dubious duo have written blockbusters before – but none as blockbusting as this wide-screen tale of alien invasion.
It's 1995, and a huge something is decelerating Earthwards. 100-odd pages pass in frenzied preparation for first contact. Most characters expect the visitors to be nice, but we know better – in a prologue, the elephant-like alien "fithp" refer to humanity as the prey.
Sure enough, when the starship Message Bearer (Thuktun-Flishithy) arrives, our orbital welcoming party gets wasted. Earth's satellite systems are polished off with dismaying efficiency. The authors hammer home the tactical advantages of space-based weaponry: anything and everything can be smeared at short notice by lasers or guided meteorites ("smart rocks"). Nuclear attack cleans out the alien beachhead in Kansas (!), only for the colonialist fithp to drop their secret weapon, the Foot. It's actually not very secret, especially if you've read Lucifer's Hammer....
With chilling enthusiasm, the authors note that their situation justifies the building of the filthiest spacecraft ever proposed: Orion. Pogoing into the sky on a column of atomic explosions, it's Earth's last chance. The final sections are thrill-a-second stuff.
This is a ripping yarn, despite typical blockbuster flaws: it takes ages to build momentum, its cast of thousands includes deadwood (e.g. some barely relevant "survivalists"), and the scope's so wide that "footfall's" megadeaths are virtually ignored. (Niven: "We'd already written similar scenes for Hammer.") The authors' enthusiasm for space weaponry comes over disturbingly strongly; one crass scene has an ecologist repenting his wicked error in opposing such plans when we were bound to have to fight aliens one day.
Against this, there's much fine stuff. The fithp themselves, offbeat herd-creatures ranking with Niven's best aliens and trying to fathom human nature by watching Deep Throat; obsessive but unobtrusive care with scientific detail; a blazing pace once the novel's achieved ignition; the crazy flight of that unspeakable, last-chance assault ship. I can even forgive Niven and Pournelle for writing themselves into a team of SF authors advising the President (correctly in every case, as it happens ...). The story's so strong that, for the duration, even this seems credible.