"You'll never think the same way about your morning cup of coffee."--Mark McClusky, editor in chief of Wired.com and author of Faster, Higher, Stronger

Journalist Murray Carpenter has been under the influence of a drug for nearly three decades. And he's in good company, because chances are you're hooked, too. Humans have used caffeine for thousands of years. A bitter white powder in its most essential form, a tablespoon of it would kill even the most habituated user. This addictive, largely unregulated substance is everywhere--in places you'd expect (like coffee and...