Kilian Jornet has conquered some of the toughest physical tests on the planet. He has run up and down Mt. Kilimanjaro faster than any other human being, and struck down world records in every challenge that has been proposed - all before the age of 25. Dominating ultra marathons and races at altitude, he has redefined what is possible in running, astonishing competitors with his near-superhuman fitness and ability. Jornet adores the mountains as fiercely as he runs them. In Run or Die he shares that passion, inviting readers into a fascinating world rich with the beauty of rugged trails and sweeping high-altitude vistas, the pulse-pounding drama of racing, and a consuming desire to tackle tests that push him to the very brink. In turns inspiring, insightful, candid, and deeply personal, this is a book written from the heart of the world's greatest endurance runenr, for whom life presents one simple choice: Run or Die.