Saville and Invisible Cities are already on my to-read list, so I'll give them a second and third respectively. Ragtime is good but I've already read it. I'm interested in both The Black Prince and Frost but since I'm about to nominate a book, I can only support one more so by a hair Frost gets a second from me.
And, I nominate
Life: A User's Manual by Georges Perec from 1978.
4.26 rating on Goodreads.
From GR:
Life is an unclassified masterpiece, a sprawling compendium as encyclopedic as Dante's Commedia and Chaucer's Canterbury Tales and, in its break with tradition, as inspiring as Joyce's Ulysses. Perec's spellbinding puzzle begins in an apartment block in the XVIIth arrondissement of Paris where, chapter by chapter, room by room, like an onion being peeled, and extraordinary rich cast of characters is revealed in a series of tales that are bizarre, unlikely, moving, funny, or (sometimes) quite ordinary. From the confessions of a racing cyclist to the plans of an avenging murderer, from a young ethnographer obsessed with a Sumatran tribe to the death of a trapeze artist, from the fears of an ex-croupier to the dreams of a sex-change pop star to an eccentric English millionaire who has devised the ultimate pastime, Life is a manual of human irony, portraying the mixed marriages of fortunes, passions and despairs, betrayals and bereavements, of hundreds of lives in Paris and around the world.
But the novel in more than an extraordinary range of fictions; it is a closely observed account of life and experience. The apartment block's one hundred rooms are arranged in a magic square, and the book as a whole is peppered with a staggering range of literary puzzles and allusions, acrostics, problems of chess and logic, crosswords, and mathematical formulae. All are there for the reader to solve in the best tradition of the detective novel.