Like the Rockefellers and the Kennedys, the Kochs are one of the most influential dynasties of the modern age, but they have never been the subject of a major biography... until now.

Not long after the death of his father, Charles Koch, then in his early 30s, discovered a letter the family patriarch had written to his sons. "You will receive what now seems to be a large sum of money," Fred Koch cautioned. "It may either be a blessing or a curse."

Fred's legacy would become a blessing and a curse to his four sons-Frederick, Charles, and fraternal twins David and Bill-who in the...