Full confession: I've read Gravity's Rainbow three times, and have never really understood it. I suspect many people can make the same statement. Strangely, I was never really bored by it, just puzzled, puzzled and dazzled. Anyway, I have just read the brilliant, staggeringly brainy, A-plus 1973 Times review by Richard Locke, which explains far more to me about this dense masterpiece than I'm willing to admit.
I am particularly impressed with his explanation of what Rilke -- among many, many others -- has to do with it.