We suspect this author might be the W. J. Hagerman who was pastor of the Montezuma Methodist Episcopal Church, Montezuma, Ohio, 1891–92. Montezuma is about 50 miles northwest of Dayton, where Tell About Jesus Today was published.
Perhaps he was minister William Joseph Hagerman (1871–1941), who is buried in Dayton?
If you can help with any of these items,