It's a great book, probably the best (or most delightful) biography I've read of anyone, in any field. It not only gives a picture of the subject as a person (as any biography should I guess), but actually engages with the person's work and gives a flavour of it — what's the point of a biography of an artist or poet that does not show their art or poetry? The "love" in the title of this book is very apt: not only did Erdős love numbers, but this a biography written with love, and the reader will love it too.