NEW YORK - When the hymn "Amazing Grace" gets to the line about saving "a wretch like me," it's not routine self-flagellation. The author of the song was a wretch indeed, a slave trader who sent some of his nearest and dearest off to be worked to death, as dramatized in the new Broadway musical Amazing Grace about John Newton, who wrote the song's lyrics as the capstone of his redemption.

That title, unfortunately, isn't the only predictable aspect of this show, whose backstory also includes the Broadway debut of Christopher Smith of Bucks County, a former suburban police officer who, seized by Newton's story, spent a decade writing the music and lyrics, and coauthored the book. After a Chicago tryout, the show opened Thursday at the Nederlander Theatre, a $16 million production featuring sea battles and storms, earnestly telling its story in the grand manner of Les Miserables.

In fact, Amazing Grace is so formulaic that you could write some of the scenes in your head before they unfold. But before the show can be pigeonholed as treacly Broadway commerce, its conceptual backbone warrants appreciation.

This tale of a rebellious young 18th-century English man who accepts slavery as part of the British Empire's landscape but then sees the error of his ways after facing a hurricane could have turned into religious propaganda. But nothing specifically denominational limits its humanitarian message of equality. The hymn "Amazing Grace," which might have been invoked throughout, instead is mostly saved for the end, similar in spirit to Candide's anthemic "Make Our Garden Grow," with kernels of the melody prefigured by the African musicians of Act II.

The score built around the title song is so functional you wonder if composer Smith was holding back to avoid detracting from its grand, climactic arrival. The music serves the plot with a selflessness that suggests this is a play with music, as opposed to a musical. That's not the way for a show to take its place among worthier Les Miz descendants.

But there's no way Amazing Grace's message will get lost, as often happens in shows that simply want to be a hit. The Chicago version was criticized for not giving the slavery issue its due. Not so here: Near the end, Newton is refused forgiveness for his betrayals - a tough, tart theatrical moment.

The panorama of characters - the Gabriel Barre- directed production has a cast of more than 30 - is well paced and well constructed but generally so risk free that even when characters start sacrificing their futures for their ideals, the consequences are minimal. Such theatrical tidiness would have mattered less if Josh Young, who plays Newton, projected some grit. But no matter how much this handsome, vocally gifted actor swigged from his flask, he remains a fresh-faced kid who fails to make you care much about his redemption, or lack of it.

As Mary, Newton's love interest, Erin Mackey is better, navigating the score's faux-Handel moments skillfully and conveying appropriate vulnerability amid her increasing sympathy for the abolitionist movement.

Most of the show's gravitas is generated by its African American cast members - Chuck Cooper as Newton's betrayed slave Thomas, Laiona Michelle as Mary's servant, and Harriett D. Foy as the imperious African princess who profits from the slave trade. If this show finds its way into the hit zone, they'll be among the primary reasons.