There are very few math books that merit the adjective ‘charming’ but
Mage Merlin's Unsolved Mathematical Mysteries (MIT Press, 2020) is one of them.
Satyan Devadoss and
Matt Harvey have chosen a truly unique, creative and charming way to acquaint readers with some of the unsolved problems of mathematics. Some are classic, such as the Goldbach Conjecture, some are fairly well known, such as the Collatz Conjecture. Others are less well known but no less fascinating – and all are intriguing and both enjoyable and tantalizing to contemplate. The authors have woven the problems into a coherent story, and I think you’ll enjoy hearing – and reading – both the story and the associated problems.