Book excerpt: Ayman al-Zawahiri--co-founder of al Qaeda and successor to bin Laden--was one of the most influential terrorists of the modern era. In the first in-depth biography of the Egyptian doctor and ideologue, Sajjan M. Gohel meticulously unpacks al-Zawahiri's long career, which spanned over 50 years, in the growth and evolution of transnational terrorism. From an illustrious Egyptian family, al-Zawahiri chose to rebel against his own society and the international order. Through his travels across multiple continents, the Egyptian found himself in many of the places where history was made. A pioneer of terrorist strategies and tactics, al-Zawahiri left an indelible legacy for al-Qaeda and other terrorists to build upon.