In Greenwich Village, not far from where Bob Dylan got his start—but in a chic Italian bistro, not a smoky dive like the late, lamented Gaslight Cafe—the Princeton historian Sean Wilentz is choking up, recalling when Dylan's new recordings began to mean something to him again, after he'd drifted away from Dylan in the 1980s.

It was 1994, and Wilentz's father, Eli, who had run or co-run the Village's Eighth Street Bookshop, a center of New York literary life from the 1940s until it closed, in 1979, was dying from lung cancer. Sean Wilentz had picked up World Gone Wrong, a CD of traditional tunes that Dylan performed on solo acoustic guitar and harmonica—a return to roots of sorts (or, some said, a confession of bankruptcy). The last song, "Lone Pilgrim," dates to the 1830s, and it begins as a visitor arrives at a grave site. It concludes with the Pilgrim himself, speaking from beyond the grave about his "Master": "The same hand that led me through seas most severe," Dylan rasps tenderly, "has kindly assisted me home."

Dylan's intimate delivery is a stark contrast to the way the song is usually sung, with the unmodulated forcefulness of the Southern rural hymn tradition from which it springs. "Dylan sings it in a very hushed way that is the man beyond the grave," Wilentz, says, after steeling himself against tears. "He inhabits that song." For a grieving son, Dylan's performance proved to be a most unexpected source of consolation—a "benediction," he calls it in his new book, Bob Dylan in America (Doubleday).

In the book, Wilentz makes the case that World Gone Wrong was also a turning point for the artist, the complete inhabitation of the old, weird songs providing a springboard for the leap into the next, fertile period of Dylan's career, beginning with the well-reviewed Time Out of Mind. "Maybe my understanding of it," Wilentz says, speaking of "Lone Pilgrim," "is it's about Dylan coming home, or to a place like home."

Wilentz's encounter with "Lone Pilgrim" was not just emotional; it led, indirectly, to a new literary sideline for a man near the top of the history profession. His renewed interest in Dylan inspired him to write an essay about the songwriter for Dissent (combining observations about Time Out of Mind and Greil Marcus's book Invisible Republic: Bob Dylan's Basement Tapes), which led to an out-of-the-blue call from Dylan's management, asking Wilentz to write some thoughts on the album Love and Theft for bobdylan.com in 2001. That led to a gig as "historian in residence" at the Web site, which led to an invitation to write the liner notes for The Bootleg Series, Vol 6: Bob Dylan Live 1964—Concert at Philharmonic Hall, a show that Wilentz had attended at age 13. The notes got him nominated for a Grammy; it pained him not to win, he admits. As late as 2006, he had no plans to write a Dylan book, and he still pleads: "Don't call me a Dylanologist!" Whatever you call his musical avocation, it's an impressive one for someone whose day job is as a respected scholar of 19th-century American politics....