This book is a classic, and deservedly so. It is comprehensive but not overloaded (like so many modern textbooks), crystal clear, well organized, rigorous. A wonderful text for teaching yourself higher math, which is how I am using it. But there is something beyond its didactic effectiveness that makes Hardy's work a must-have for anyone interested in math: This is a truly beautiful book, and working through it, while by no means easy, is an intellectual and aesthetic delight of the first order. Hardy is a genuinely elegant, subtle, incisive thinker, and his unbounded enthusiasm for his subject, duly controlled by British understatement, shines through every page. He conveys the irresistible, almost addictive quality of math.