One of the main arguments of my forthcoming religious biography of Ben Franklin is that key relationships with evangelicals and Calvinists, like the revivalist George Whitefield, tethered the skeptical Franklin to the Puritan faith of his upbringing. One of the most important tethering relationships for Franklin was with his evangelical sister Jane. I first encountered Jane (Franklin) Mecom in Jill Lepore’s marvelous Book of Ages: The Life and Opinions of Jane Franklin.

Lepore details Ben and Jane’s lengthy correspondence, pondering the ways in which the circumstances of history allowed the bright boy Ben to pursue fame and scientific knowledge, while Jane married at 15 and lived a family life that was rich in relationships but also full of strife and struggle. (Many children and grandchildren preceded her in death, and her husband was constantly in debt—any knock on the door might be a collections officer come to take more household items, or to take him to to debtors’ prison.)

Harvard’s Lepore is one of the finest prose stylists among American historians today, and this is a book that you can’t skim even if you want to. This is what Lepore does best: painting vivid pictures of lives and conflicts in the past, and raising provocative issues about the meaning and methods of history.

In the case of Jane Franklin, she confronts the perennial question of why most people—especially women and the poor—never get mentioned in history, while the Ben Franklins of the world get innumerable books written about them. The most obvious answer is sources, and Lepore goes to great lengths to show why so many of Jane’s letters—even ones written to Ben—did not survive, while Ben’s did.

Yet in many ways, Jane’s life, not Ben’s, was representative of the age. Ben presented himself as the American everyman in his autobiography, but Jane was, as Lepore puts it, “everyone else.” If I have a criticism of the book, it is that Lepore may downplay an aspect of Jane’s life that made her so representative: her Christian, and especially Calvinist convictions. Lepore spends much of the book squinting to find hints of independent or even feminist thought in Jane’s “opinions,” when what struck me were the articulated opinions reflecting biblicism and Calvinism.

Lepore suggests that those views, especially Jane’s strong convictions about God’s sovereignty, gave her a sense of dignity but also passivity in the face of her suffering and mundane existence. But I wanted to know more about her Christian “opinions,” revealed for instance when she interacted with her skeptical brother about Jonathan Edwards’s Some Thoughts Concerning the Present Revival of Religion.

I and others have emphasized the contrast between Ben Franklin’s self-professed Deism and his longtime friendship with the Calvinist evangelist George Whitefield, but Lepore convinced me that his sister’s influence likely had an even stronger tethering effect connecting Ben to the faith of his childhood. This makes more sense of why Franklin the Deist was the one calling (futilely) for the Constitutional Convention to open its sessions in prayer in 1787.

While Lepore may emphasize different aspects of Jane’s life than I would have, I recommend her book as a delightful read, a model of historical reconstruction, and an essential work for understanding Ben Franklin and his fascinating sister.

This post originally appeared at the Anxious Bench blog, Patheos.