Rediscovering Jacob Riis: Exposure Journalism and Photography in Turn-of-the-Century New York, by Bonnie Yochelson and Daniel Czitrom, The New Press, $35.

In his autobiography, Jacob Riis tells of being so inspired by a sermon from a local preacher that he considered abandoning journalism and becoming a minister himself. "We have preachers enough," was the advice he received. "What the world needs is consecrated pens." He took this to heart. "Then and there, I consecrated mine," he wrote. Year later, Riis would refer to his slideshow lecture on the ills of urban life as a "lay sermon" — one that always ended with an image of Jesus Christ.

That slide is lost. But nearly 120 years after the publication of Riis' other slides in "How the Other Half Lives," two authors have turned again to the book that heralded the Progressive Era and shaped how generations think about cities. In "Rediscovering Jacob Riis: Exposure Journalism and Photography in Turn-of-the-Century New York," Bonnie Yochelson and Daniel Czitrom extricate Riis from the hagiographic narratives built up around him as photographic pioneer and "the best American" Teddy Roosevelt "ever knew," and meticulously reconstruct the details of his practice as a photographer, his personal motivations and the historical and political context in which he worked.

The title of Riis' epochal work concealed one of his wry jokes: As Riis made clear in the book's introduction, in 1890 when the book was first published, the "other half" had swollen to three-fourths of New York City's population. According to Riis' figures, more than 1.2 million people were crammed into 37,000 tenements. While the law defined a tenement as any building "occupied by three or more families, living independently and doing their cooking on the premises," Riis saw a starker reality—of a family in "one or two dark closets, used as bedrooms, with a living room twelve feet by ten…" and of four families sharing a floor.

"How the Other Half Lives" was arranged as the sort of "slum tour" popular among the era's enlightened upper class, with Riis leading the reader from one ethnic neighborhood to another, from tenement to tenement, stopping along the way to observe the particular problems posed by children, paupers, drunks and an assortment of other urban types. The book was an instant bestseller and went through multiple editions; it was still in print when Riis' died in 1914, just short of a quarter-century after its initial release.

As Yochelson and Czitrom make clear, the structure of Riis' book reflected the form in which the photographer's raw material was originally presented. Riis first used the photographs of "How the Other Half Lives" in what was known as a "lantern slide lecture." At the time, lectures exploiting new slide projection technology had become popular entertainments; Riis hoped to join the lecture circuit and galvanize his audience into action.

Riis had lived in the slums himself when he first arrived in New York, and then covered the city's tenements as a reporter for 13 years before writing his book; he earned his outrage at the conditions there firsthand. But Czitrom's work in particular highlights another important contributing factor to Riis' crusading spirit: His conversion to Methodism early in his career. Indeed, Czitrom writes that when, "Riis took his [slide] show on the road… [he appeared] almost exclusively before Christian audiences at churches and YMCAs."

But Riis' embrace of the Christian community was selective. "Riis was disillusioned by most clergymen in New York," says Tom Buk Swienty, a Danish reporter and the author of a forthcoming biography of Riis, "because they did not open their churches to his lantern-slide lectures out of fear that this would be too radical and morally corrupting for a God-fearing Protestant audience to see." Riis' own church withdrew an invitation for Riis to speak, and Yochelson notes that Riis resigned as a deacon in protest.