This is the improbable story of how Ultra-Trail du Mont-Blanc (UTMB) became one of the world's great sporting events, even as it set new limits of human endurance. It is a story of how world's best runners, in the historic home of mountain adventures, brought about a revolution in running that has been felt across the globe. For this unbiased and inside look at the past, present and future of the UTMB, author and trail runner, Doug Mayer, was given unfettered access to the UTMB archives, and spoke to more than 100 people, from race organizers and winners, to experts and scientists, to those who love the UTMB, and even those who hate it. The result is a book with more than 200 photos, maps and infographics that is the most comprehensive perspective into trail running's greatest race. With an estimated 20 million participants since 2010, trail running has been one of the world's fastest growing sports, according to the International Track and Field Federation. In 2023, 25 races around t