There's a popular edition of Gravity's Rainbow ("Penguin Classics Deluxe Edition, white A4 rocket pointing down on the cover) that, for some pressings at least, is a pretty poor print. Missing lines, haphazard paragraph breaks, etc. Given the writing style, I'd recommend any other edition (Penguin 20th century is good, blue cover with rocket schematics) to make it less of a challenge to read.