99 Variations on a Proof is a mathematics book by Philip Ording, in which he proves the same result in 99 different ways.
The structure of the book was inspired by Oulipo co-founder Raymond Queneau's Exercises de style (1947).
Writing in The Mathematical Intelligencer, John J. Watkins described the book as "marvelous" and said that "Ording's inventiveness seems boundless".
[1] While Watkins found the origami-based proof in Chapter 39 perplexing, Dan Rockmore's review in the New York Review of Books called the same proof "a delight".
[2] Reviewing the book for the Mathematical Association of America, Geoffrey Dietz also gave a positive evaluation, saying that he "learned something new" from several proofs and found some of them quite comedic.