An affectionate if impressionistic portrayal of one of the century's greatest and strangest mathematicians. Though little known among nonmathematicians, Erdâ€¦s, who died in 1996 at age 83, was a legend among his colleagues. According to Hoffman (Archimedes' Revenge, 1988), the Hungarian was so devoted to mathematics that he went without wife, children, steady job, or even a home, preferring to exist as the wandering guest of fellow mathematicians. He lived for math, announcing his visits with a hearty, ""My brain is open,"" posing and solving problems while subsisting on amphetamines and coffee ("" 'A mathematician,' Erdâ€¦s was fond of saying, 'is a machine for turning coffee into theorems' ""), and forgoing pleasantries like ""Good morning"" to jump right in with, ""Let n be an integer."" He published more than 1,500 papers with at least 484 coauthors, who pride themselves on their ""Erdâ€¦s number of 1"" (a figure indicating one's degree of separation from the master). Hoffman, who traveled with and interviewed many of his collaborators, weaves oral histories and clear mathematical explication into a digressive (sometimes too digressive), entertaining whole. Hoffman creates a full-bodied and eccentric character out of hundreds of quotations and anecdotes. Missing are the linear landmarks of conventional biography: Erdâ€¦s doesn't get born until page 48, a precise account of his death is absent, and his most important mathematical discoveries are nowhere summarized. Though a biography, this book works like the best fiction, finding in a concrete universal to show what mathematics is and who the people are who uncover its truths.