By Sarah Vowell. Riverhead, 272 pp, $28.50, hardcover

Reading The Wordy Shipmates, the latest book by New York’s Sarah Vowell, is like watching a film with an overly sarcastic commentary track, or going to a museum with someone who makes fun of all of the exhibits. Vowell clearly has great affection for her subject—the fanatically devout Puritans who founded the Massachusetts Bay Colony in the 1620s—but barely a page goes by without some snippy interjection that grinds whatever narrative force she has built up to a lurching halt.

“The country I live in is haunted by the Puritans’ vision of themselves as God’s chosen people,” she writes, “as a beacon of righteousness that all others are to admire.” Vowell’s aim is to provide a breezy, informal comparison between this inherited legacy and what the Puritans actually stood for, and to do so, she draws from the multitude of books, journals, pamphlets, and other writings they left behind. Her particular focus is on Gov. John Winthrop and the two perpetual thorns in his side, Anne Hutchinson and Roger Williams, both of whom felt that Winthrop, leader of the dangerous voyage across the Atlantic to get away from the Church of England, wasn’t quite Puritan enough.

It’s a fine story to tell, but Vowell’s first-person digressions litter the pages like land mines, with her penchant for contemporary pop-culture parallels the most flagrant (but by no means the only) offense. Perhaps a book about 17th-century Puritans shouldn’t reference the Rolling Stones, Spider-Man, The Godfather Part III, and the New York Times real-estate section—at least not all within its first five pages.

Then there’s the more pressing question of why this book exists at all. Surely Vowell isn’t the first person to write about the colony next door to the more famous Plymouth Pilgrims, and an academic study would have to round out the corners of this vintage slice of Americana with far more depth and rigour. The Wordy Shipmates is frustrating even as popular history, though its lesson is clear: this kind of work should be left to the professionals.