Mr. Armstrong received a diagnosis of testicular cancer in fall 1996. The disease spread to his brain and stomach. With his chances of survival put at less than 50 percent, he underwent surgery and chemotherapy.

Image Juliet Macur Credit... Andrew P. Scott

As he recovered, he formed a cancer charity that would bring in millions of dollars in contributions through the sale of yellow wristbands with the word “Livestrong.” By January 1998, he had joined the United States Postal Service Pro Cycling Team. He began his string of Tour victories a year later.

“He had risen from his deathbed to a secular sainthood, and Americans were all but salivating to claim him as their own,” writes Ms. Macur. “He was someone the country could cheer for and be proud of, a man on a classic hero’s journey that had all the elements of a boy-done-good story.”

“Cycle of Lies” is a scrupulously reported and sourced book. In addition to the one-on-one cooperation Ms. Macur received from Mr. Armstrong, she went to some lengths to bring in other voices, many of which corroborated the rumors that had surrounded Mr. Armstrong for years but that he had aggressively disputed. She was granted access to 26 hours of private recordings by J. T. Neal, a wealthy Texan who befriended Mr. Armstrong as a teenager and became a mentor and father figure to him.

She also obtained interviews with other key insiders who had not spoken to the news media before. During Mr. Armstrong’s racing days, cyclists and others who were close to him observed a code of silence. Coded language was used whenever the subject of EPO came up. They called it Edgar Allan Poe or just Poe. In fear for their careers and of the power Mr. Armstrong held over them, his teammates accepted the moral relativism in which he cloaked his doping practices: How can it be called cheating if everyone does it? And he continued to remind his teammates that everyone did.

So the lying began at the Tour in 1999. “After that, he says, he could never turn back — he had to keep denying,” Ms. Macur writes. Admirers who stood by Mr. Armstrong for 14 years could not conceive that anyone who had survived cancer would place himself in jeopardy by doping. Mr. Armstrong lashed out at anyone who doubted him, particularly reporters who did not buy into the spin that he and sponsors promoted.

One sponsor, Nike, even ran a commercial in which Mr. Armstrong says: “Everybody wants to know what I’m on. What am I on?” He says he’s on his bike six hours a day, and then asks, “What are you on?”