Donald Miller seems an unlikely evangelist—at least by conventional standards. In his books Through Painted Deserts (a revision of Prayer and the Art of Volkswagen Maintenance, 2000) and Blue Like Jazz (2003), the former youth pastor sets out from Houston on a cross-country drive, settles in Portland, audits classes at the proudly bohemian Reed College, and spends many sentences distancing himself from fellow evangelicals when he believes they are too entangled with the Republican Party.

But on other pages of Blue Like Jazz, Miller describes how he and fellow Christians set up a "confession booth" during Reed College's Ren Fayre, a weeklong college-approved drunken revelry. Miller and his friend Tony dressed like monks and took turns sitting inside the booth. Here's the kicker: the young Christian students confessed their sins to their perplexed and then intrigued classmates.

A similar vulnerability marks all of Miller's books, including Searching for God Knows What (2004) and To Own a Dragon (2006), in which he shares author's credit with John MacMurray, a Multnomah Bible College professor who welcomed Miller into his family home for four years. "The voice is mine, but the wisdom is John's," Miller says of their collaboration.

Miller's honesty and self-effacing style keeps him busy as a guest speaker at events ranging from large (an international Mothers of Preschoolers convention) to intimate (talking about sexual purity with fraternity members at the University of Texas).

"I seem to enjoy medium-size venues, 300 or 400 people, that tend to lean academic," Miller says, telling Today's Christian about his favorite setting for speaking engagements. "I also really like groups of college students who are not Christians. A mixed group of Christians and non-Christians is usually fun. It tends to create the most tension."

Like jazz music, which, as Miller observes at the beginning of his book, sometimes doesn't resolve, faith in God is full of unresolved questions. It's this offbeat metaphor of the Christian life that drives the personal essays in Blue Like Jazz. The unexpected success of the book (fueled primarily by word of mouth, it has sold more than 800,000 copies) has given Miller a platform to share the Christian story with both non-believers who are suspicious of religion and spiritually hungry folks who are cynical about today's evangelical institutions. His appeal is probably rooted in Miller's skepticism about man-made formulas and systems constructed around contemporary faith in Christ.

"Because we live in a constant sales environment where we are told a certain car will make us sexy or a certain dishwashing detergent will be a miracle for our dishes, we assume the gospel of Jesus works the same way, that is, if we invest something, we get something more back," he observes on his website. "But this is not the case. … When we let go of the idea of Jesus as a product and embrace Him as a being, our path to spiritual maturity begins."

Miller says his Christian and non-Christian readers often have lingering stereotypes about one another. He enjoys defanging those stereotypes, like a stand-up comic, by joking openly about them. For instance, he says, Christians may see their non-Christian neighbors as anti-authority, anti-morality, and thriving on chaos, while non-Christians see Christians as simple-minded, consumerist, and reliably pro-military. Let's just lay down those stereotypes out there in the open, he says, so we can move beyond them.