Edition: Jonathan Cape, 1973
Twenty-five years on, this book is something of a classic of the underground hippie scene, though perhaps not on the scale of Pynchon's earlier V. It's written in a complex stream of consciousness style, which is quite hard to read until you begin to get into it; I'm not sure that I understood much of what was going on even when I got to the end of the 760 pages. It's not really about understanding what's going on; Gravity's Rainbow presents an experience which is not intended to be completely assimilated.
The main plot concerns the German wartime rocket development, and one of the major themes of the novel is the psychic effects the idea of the rocket had and has upon people. The main character, Tyrone Slothrop, has a particularly strong connection to the rocket, one noticed by British intelligence when they discover that the map on the wall of his office detailing his sexual conquests exactly matches the mathematically random (and therefore unpredictable) scattering of V2 impacts across London but a few days in advance. (I think it is this scattering which gives the novel's title, but this is not made explicitly clear.) The connection between his sexuality and the penile nature of the rocket is clear. As the war comes to a close, Slothrop is selected for a mission to discover what has happened to the rocket serial number 000000, which has disappeared. This rocket is rumoured to be some kind of super-rocket, something really special. As Slothrop's search goes on, he beomes more and more obsessed with the rocket, to the point of dressing up as the character Rocketman. He becomes a mythical figure in the Zone, which presumably refers to the American zone of occupied Germany. If the structure of the book leads to comparison with Ulysses, the obsessive nature of the search is like that of Moby Dick; both these novels are name-checked in the quoted review on the back cover.
There are independent deviations from the main plot, mainly taking the form of short (often ribald and obscene) anecdotes or fables. My favourite among these included the German spa resort of Bad Karma; the woman with a speech defect unable to pronounce umlauts, so pronouncing a warning about a "cute burglar" as "lift screwer" and inspiring an engineer who overheard her with the name for his new invention, the helicopter; and the story of Byron the immortal lightbulb.
Altogether, Gravity's Rainbow takes some getting into; it helps distinctly if you have some knowledge of engineering mathematics. It is not a novel for the prudish, but for those who are not and who are prepared to make the effort it is very worthwhile.