On May 13, 1913 Sikorsky became the first person to pilot a four engine aircraft.
On May 24, 1940 he performed the first successful single-rotor helicopter flight.
Sikorsky's autobiography, The Story of the Winged S. (originally published 1938; updated editions, various years up to 1948)
Frank J. Delear, Igor Sikorsky: His Three Careers in Aviation (New York, 1969) - described as "the only biography"
Igor Sikorsky article from ctheritage.org (reference)
Biography from Sikorsky company