Peter Thiel, Elon Musk, and the rest of the "PayPal Mafia" are now household names who've reshaped technology, automobiles, space travel, and politics. But two decades ago, they were unsung entrepreneurs attempting to launch a Silicon Valley startup against overwhelming odds. That improbable journey started in the shadow of Stanford University, when Thiel met Max Levchin, a Ukrainian engineer who recently moved to California. Years before...