For Pam Reed, a marathon is nothing — a morning warm-up before starting her day. Running through a desert for 28 hours in temperatures so hot the asphalt melts your Nikes? Now that's a race.

As she tells it in her new autobiography The Extra Mile (Rodale), Reed helped put ultrarunning on the extreme-sports map. In 2002 she became the first woman ever to win the Badwater Ultramarathon, a brutal 135-mile race across Death Valley in July. In 2003, she beat out all 80 competitors again and remains the only woman with the first-place title.

Last year, Reed became the first person to run 300 miles nonstop with no sleep. She holds the U.S. women's record for running the most miles in 24 hours (138.96), and she once completed the London Marathon and the Boston Marathon (she has run the latter twice) in 48 hours.

Is she crazy? "Maybe a little," says Reed, laughing. However, the 100-pound mom prefers the word "driven." "When a race is over, I'm definitely happy," she explains, "but within a couple of days or even an hour, I want to do it again. I want to see if I can do better."

In her book and in conversation, Reed comes off as complex, intense, even contradictory. She describes herself as an easily bored type A, yet she'll gladly run laps around the same quarter-mile track for two days straight. She claims to compete only with herself but has taken flack for supposedly dueling with 2004 Badwater champ Dean Karnazes.

Reed credits ultrarunning with healing her relationship with food. For 15 years, she battled anorexia. "I look at food now as fuel," says the former triathlete, who ingests Ensure, Red Bull, noodles and oatmeal during a race (often while running). "If I don't eat, then I can't do what I want to do. I see food now as a positive thing."