Which is the best earning book in the world ?
As of my knowledge cutoff in September 2021, the best-earning book in the world is widely considered to be "Harry Potter and the Philosopher's Stone" by J.K. Rowling.
The success of the Harry Potter series as a whole has been staggering, with millions of copies sold worldwide and numerous translations into different languages.
However, it's worth noting that book sales and earnings can change over time, so it's possible that newer books have achieved significant success since then.
It's always a good idea to check the most recent information to get the most accurate and up-to-date answer.