This post is about two popular-mathematics books the I recently read:

### MY BRAIN IS OPEN: The Mathematical Journeys of Paul Erdős / Bruce Schechter

On one occasion, Erdős met a mathematician and asked him where he was from. “Vancouver,” the mathematician replied. “Oh, then you must know my good friend Elliot Mendelson”, Erdős said. The reply was “I AM your good friend Elliot Mendelson.”

Several years ago I read another biography of Erdős by Paul Hoffman, which was nice, though focused mainly on Erdős’s eccentricities. I think that Schechter’s biography would appeal more to mathematicians, since it consists of a lower dose of eccentricities and of a higher dose of details about the mathematical world. For example, it was very interesting to read about how a Hungarian mathematics journal for high school students helped in the nurturing of many great mathematicians, and about the events that led to the elementary proof for the prime number theorem by Selberg and Erdős. I definitely recommend this book.

For those who are looking for an even lower dose of eccentricities and more details about the mathematical world, I recommend the piece “In and Out of Hungary, Paul Erdös, His Friends, and Times” by László Babai. It can be found in volume 2 of Combinatorics, Paul Erdös is eighty, and it contains many details about the Hungarian mathematical world (and about 20-th century Hungarian history in general).

### Mathematical Cranks / Underwood Dudley

Represent heaven, the home of God, as a vector space of infinite dimension over some field known to god but unknown to us, in which the activities of God are quantifiable. Lengths will be measured (Revelation chapter 21 verse 15) in the usual way, as the square roots of the inner self-products of vectors (assuming heaven to be euclidean).