Ask HN: Casual Math Book Suggestions

Colossal Book of Mathematics by Martin Gardner: Uses games and recreational math to introduce areas like group theory and topology.

"The Great Mathematical Problems" is about reading a chapter, then taking a rest, then reading another.

The Great Mathematical Problems by Ian Stewart: Does a good job explaining several of the major open problems in math today.

I enjoyed T. W. Körner's The Pleasures of Counting

Finding Moonshine by Marcus Du Sautoy: Tells the story of the unexpected connection between two areas of math that, on the surface, seem to be completely unrelated.

I’ve read about 15% - 20% of Imaginary Numbers are Real. It’s a great book, so far.

His "Nature of Numbers" is exactly that, also this is the first English book (foreign language for me) which I have read without any need of dictionary.