We all know the textbook-burnished image of Thomas Alva Edison -- the indefatigable genius who gave us the lightbulb, the phonograph, and other life-altering inventions. Less remembered but equally fascinating was his bitter and very public feud with George Westinghouse over which electrical delivery system would be adopted by America and, by extension, the world. In a morally unsettling attempt to prove the risks of Westinghouse's technology, Edison (a onetime opponent of the death penalty) advocated using the rival system as a means of execution. Westinghouse eventually won the day, as does Essig in his engaging and meticulously researched book. Part history, part science primer, part meditation on capital punishment (the harrowing eyewitness accounts of the first state-sanctioned electrocution are unforgettable), ''Edison & the Electric Chair'' delivers a thrilling jolt of discovery.