For over half a century, at almost any hour of the day, mathematicians the world over might answer a knock at the front door to find a short, frail man wearing thick eyeglasses and a rumpled suit, carrying a suitcase containing all his belongings in one hand and a bag full of papers in the other, who would announce, "My brain is open! " The visitor was Paul Erdos, one of the greatest mathematicians of the twentieth century and certainly the most eccentric. Having no home or job, and incapable of the most ordinary household tasks, Erdos was sustained by the generosity of colleagues and by his own belief in the beauty of mathematics. Erdos believed that the meaning of life was to prove and conjecture. He was fascinated by numbers and became one of the century's leading numbers theorists. He worked in fields of mathematics that would prove pivotal to the development of computer science, even though he had never touched a computer. He was the most prolific mathematician who ever lived, writing or collaborating on more than 1,500 papers with over 450 different collaborators. Witty, filled with the sort of mathematical puzzles that intrigued Erdos and continue to fascinate mathematicians today, My Brain Is Open is the story of this strange genius, and a journey in his footsteps through the intriguing world of mathematics, where universal truths await discovery like hidden treasures and where brilliant proofs are poetry.