I recently learned of the existence of the Cain’s Jawbone book 📚. It’s a murder mystery novel written in 1934.
However, the 100 pages of the book come to you arranged in the wrong order. To solve it you have to figure out the order they should be in. The number of possible combinations is a number with 158 digits.
Originally one could win a prize for doing so - £15 in 1934, and £1000 more recently after it was re-released.
Apparently it’s only known to have been solved 4 times ever so far, the solution being almost the only thing not yet available for download on the internet.