Amazing Grace is an unforgettable hymn, promising balm to every troubled soul ever since a British cleric composed it in 1722. You can hear it in your mind right now—perhaps an echo of civil rights demonstrations, anti-Vietnam war rallies, Judy Collins' acapella recording in 1970, or President Obama turning to God's comfort in the aftermath of a racist murder at a Charleston church.

Coming in October are two books that stand on the hymn's message of the unearned favor and forgiveness God offers all sinners: Amazing Grace: A Cultural History of the Beloved Hymn, (Univ. California Press) by historian James Walvin, and a newly revised and updated edition of Phillip Yancey's award-winning bestseller What's So Amazing About Grace (Zondervan).

Walvin, who has written extensively on the political and social impact of slavery, details the life of the hymn's author, John Newtown, a brutal slave ship captain who studied theology by night while delivering his captives to the auction docks. He didn't quit the slave trade for shame, as some urban legends say, but rather had a stroke that ended his ability to go to sea. In Newton's papers, Walvin found that Newton condemned himself as a depraved libertine, writing that it was only "Amazing Grace that snatched me from ruin, that pardoned such enormous sins, preserved my life when I stood upon the brink of eternity and could only be preserved by miracle.”

He then became a cleric and hymnist, sharing the gospel at a rural English church. Although he did eventually testify against the slave trade before Parliament, "Amazing Grace was not written by John Newton the abolitionist," Walvin writes. It was written "to win over doubters, to strengthen the wavering, and to sustain the faithful."

Once the hymn reached America, it spread rapidly. The Library of Congress has 3,049 recordings in a special collection. In his book, Walvin details the song's movement through churches Black and white, through funerals and celebrations, and out into the world of popular culture as the modern music industry capitalized on a song that was simple to sing and free to record. Amazing Grace also focuses on how musical versions became chart-topping mass-market hits.

Meanwhile, PW finds, scores of authors and publishers—spiritual and secular—have turned in recent decades to the eye-catching, heart-touching phrase for book titles from spiritual bestsellers, scholarly works, children's books, and even coloring books.

When Yancey first wrote What's So Amazing About Grace, he said that through his life "marked by wanderings, detours, and dead ends, I see now that what pulled me along was my search for grace." It was named Book of the Year by the Evangelical Christian Publishers Association in 1998. In 2006, it ranked 17th on Christianity Today's list of most influential books for evangelical readers.

Yancey writes in his new introduction that he returned to the book a quarter-century later because, in contentious times of deep s divisions, "...We can choose to withdraw, hunkering down with like-minded people. Or we can choose the Jesus way, seeing schism and antagonism as a testing ground for grace."

The revised version updates examples and references in the original text, bringing in modern examples like the comment U2 lead singer Bono made after he studied the book with his band. The singer writes: "When you boil it down, the universe runs by either Karma or Grace. I'd be in big trouble if Karma was going to finally be my judge. I'm holding out for Grace."

Spiritual writer Kathleen Norris also used the hymn as a title for her 1998 book, Amazing Grace: A Vocabulary of Faith. But, she tells PW now, that was not the original title she proposed for an examination that featured chapter headings such as "fear," "damnation" and "hell. "I was going to call it Scary Words, which my publisher hated. I was struggling for the right title when 'grace' occurred to me. It's a hymn so well known and loved and it can be found in every life."

For her chapter on grace, Norris paraphrases, Psalm 139. She wrote that it tells readers that "darkness is as nothing to God who can look right through whatever evil we've done in our lives to the creature made in the divine image." In Norris' book, no matter where we run or hide, she writes, "God will find a way to let us know that he is with us in this place, wherever we are, however far we have run."

In the decades since Norris first wrote those words, not much as changed. She says, "God has to put up with a lot from us — bad preaching, indifferent pastoral care, dreary Sunday mornings church with a choir with about three people who can actually sing. But it is a community turning to God. And God gave us a voice so that's God's fault anyway. So, I sing away even when the organist is playing the wrong chords. The hymn Amazing Grace was a blessing from a man who had made a mess of life. Once you hear it, you can't unhear it."