King of the World by David Remnick is a thorough book subtitled Muhammad Ali and the Rise of an American Hero. Written in 1998 by the longtime New Yorker editor, the book focuses on Ali's life up until the time that his title stripped and ability to box professionally taken away following his refusal of military service during Vietnam.
Ali was born Cassius Clay and grew up black middle class in Louisville, Kentucky. He was as a talker from a young age and his bicycle stolen when he twelve, leading to a kindly police officer who ran a local gym suggesting to Clay that he learn how to fight, and then training him. Clay was blessed with size and quickness, and also worked extremely hard at the craft of boxing. He never smoke, never drank, and just trained to build his body up. He talked about how good he was, how he would be champion of the world someday, and was by all accounts a nice kid, not a bully. He entered the main black high school in 1957 for the 10th grade, and wasn't a good student, but the principal liked him and sent him through, saying that he was going to be a great boxing champion. By the age of eighteen, Clay had an amateur record of 100 wins and 8 losses, and two national golden gloves championships.
Clay won a gold medal in the 1960 Olympics in Rome and then turned pro. Remnick in the book provides great detail about what a force of nature Clay was in his late teens and early twenties, both in terms of physical prowess and showmanship. Related to this, it was interesting reading about the influence sportswriters had in crafting narratives to the public, and most didn't like Clay due to his bombastic personality. When he was in high school, Clay had wanted to write a term paper on the Black Muslims and in his early twenties, he heard about Elijah Muhammad and the Nation of Islam that he the leader of. Clay was a searcher, and in the Muslim religion he found something that resonated with him, and became close with one another Nation of Islam leader, Malcolm X.
Clay's first fight for the heavyweight title was against Sonny Liston in February 1964 and few expected Clay to win the fight, with Liston viewed by many as an unstoppable force. Clay defeated Liston and very shortly after confirmed that he had become a member of the Nation of Islam, also noting that Black Muslims wasn't a real thing, rather a word made up by the press. Once Clay won, Elijah Muhammad welcomed Clay into the fold, his fold. On March 6, Elijah Muhammad gave a radio address and said that Muhammad Ali would be the boxer's new name. Elijah Muhammad had begun to view Malcolm X as a rival for power within the Nation of Islam, speaking in favor a civil rights bill, and working with Martin Luther King, whom Elijah Muhammad wanted to not associate with. As a result, Malcolm X was cast out of the Nation, and Ali no longer talked with him.
The rematch between Muhammad Ali and Sonny Liston was to be in November 1964, but three days before the fight, Ali got a hernia, and the fight rescheduled for May 1965. Malcolm X was killed in February 1965 and Ali dominated Liston in the fight, knocking him out in the first round, leading to the famous photo of he standing over the fallen boxer. Later in the year Ali fought and defeated Floyd Patterson and three months after that began his battle with the US government over Vietnam. He was reclassified so that he could be drafted and said that he had no quarrel with the Vietcong. He started speaking out against the war and said that he wouldn't simply fight exhibitions for the government to satisfy his service requirement. In April 1967 he appeared at a US Armed Forces location where he had been summoned, and said that he was refusing draft orders as a minister of the religion of Islam. He was sentenced to five years in prison and a $10,000 fine.
The Supreme Court would clear him in 1971, but he didn't box for three and a half years, and then regained the heavyweight championship in 1974 against George Forman in Kinshasa, Zaire. By the time of his final bouts in 1981 his neurological decline, eventually to become Parkinson's, had almost certainly begun already. Ali later in his life greatly regretted his casting aside of Malcolm X and died in 2016 at seventy-four.