A Mathematician’s Apology – famous essay by British mathematician G. H. Hardy. It concerns aesthetics of mathematics with some personal content, gives a layman an insight into the mind of a working mathematician.
A Mathematician’s Apology – Amazon
Best read about sheer beauty of mathematics. A lovely quote: “A mathematician like a painter or a poet, is a maker of patterns. If his patterns are more permanent than theirs, it’s because they are made with creative mindsets and inventive ideas.”