Sarah Vowell is in rare company when it comes to her ability to craft a biting, funny sentence. She’s up against David Sedaris and Jincy Willett and a small handful of other names. Consider this line from her latest book, Lafayette in the Somewhat United States:

“I do not think that there can ever be enough books about anything; and I say that knowing that some of them are going to be about Pilates.”

It’s poetry of a sort: that generous and promising opening, followed by a long rest on the semicolon and a quick veer into misanthropy on the very last word. Her paragraphs frequently take on the same form, beginning in magnanimity and ending with a surprising sharpness. Here’s Vowell in the same book, writing about her first and only time attending a Quaker meeting:

I sat there for two hours and no one said a thing. Or rather I thought it had been two hours when in fact I lasted precisely fourteen minutes. Not because it was boring, but because it was the opposite of boring—tense, in fact. At one point I crossed my legs and the sound of denim on denim was so loud, my knees seemed to be plugged into some imaginary amp. Which did make me appreciate how growing up in this hushed Quaker atmosphere could make a person denounce war for purely acoustic reasons. If the noise of one antsy visitor squirming in her seat was that jarring, how evil must actual gunfire sound? In the meeting, I found myself wishing for something interesting to listen to that might also drown out the ambient sneezes, as well as something we could all look at to avoid the awkward eye contact. I left when I realized that sort of communal spiritual experience does exist. It’s called the movies.

She begins with an account of religious exploration, expands into an uncomfortable anecdote, theorizes about the origins of one of America’s longest-standing pacifist traditions, and then admits she’d rather be at the multiplex. A less-talented writer would push that final turn into the word “movies” as something cruel, or showy, or uncomfortable, but Vowell just drops it there and lets it sit. It’s not an indictment of Quakerism. If anything, Vowell is the butt of her own joke, the “antsy visitor” who fails to understand what the big deal is and gives up early, opting instead for the latest James Bond movie down at the mall. It takes real talent to be this mean and this big-hearted at the same time.

Vowell’s latest book tells the story of the Marquis de Lafayette, the young French general in George Washington’s army who became a hero of the American Revolution. It includes a generous dollop of contemporary anecdotes but it’s more-or-less straight history, following more in the tradition of her The Wordy Shipmates and Unfamiliar Fishes than the blended comedy-and-history of The Partly Cloudy Patriot and Assassination Vacation.

Lafayette is a good choice for the subject of a book. In a time when France is consistently mocked as the wishy-washy, socialist, surrender-happy opposite of everything America believes itself to be, Lafayette is a reminder that there was a time at the beginning of our national story when the French saved our collective American bacon. And Lafayette was celebrated across the nation — in “a euphoric thirteen-month victory lap in which Lafayette toured all of the then twenty-four states” — as a national hero and one of our very first celebrities.

Vowell contextualizes Lafayette’s story by employing the half-assed Revolutionary War education we all received in elementary school, positioning him around and among the Founding Fathers (the general was a huge George Washington fanboy, even naming one of his children Georges Washington de Lafayette.) She visits a few Revolutionary landmarks including Colonial Williamsburg, and she tries to tie Lafayette’s story, with varying success, to contemporary events including the 2013 government shutdown and the grandiose wave of anti-France sentiment that swept the nation following the American invasion of Iraq. (Remember freedom fries?)

This is not a dip into the shallow end of history. Vowell uncovers some deep cuts, including France’s comptroller general of finance, Anne-Robert Jacques Turgot, who predicted the end of colonialism hundreds of years early. Nations like France, Turgot foresaw, would “see their colonies escape them all the same, and become their enemies instead of remaining their allies.” Vowell draws a straight line from Turgot’s observations to the collapse of France’s involvement in Vietnam. These little discoveries are fascinating additions to our understanding of history, and Vowell delivers them with a no-big-deal, conversational tone.

Unfortunately, Lafayette is only a qualified success. It carries the same fault as all of Vowell’s most recent historical texts, which is that she doesn’t quite manage to make history break out into song. Vowell’s history remains locked in the past tense, more academic than narrative, a collection of scenes with no biographical drive. The book is fun, and undoubtedly funny, but it doesn’t tell a complete story with a beginning, middle and an end. It’s just a bunch of (well-written) stuff that happened, with some modern-day interjections.

Vowell’s most satisfying book to date is still Assassination Vacation, because it perfectly synthesized the pop cultural vibrance of her first couple books with the vigorous historical nerdery of her later work. Vacation had a narrative arc and a storytelling ambition that Vowell’s most recent three books have not enjoyed. Lafayette feels as though Vowell entered the book with a thesis in mind, and then she set to work proving that thesis, ignoring anything that did not suit her worldview. There’s very little spontaneity here, just an outline padded out with a generous hunk of research and some very witty observations.

“America’s funniest historian” is an important role to fill, and Vowell is unquestionably the person to fill it. We need someone to remind us that the Founding Fathers were not idols carved from granite; they were people, as real and as ridiculous as you or I. But Vowell needs to become more comfortable breathing life into her characters, rather than just telling us what they did and said. She never quite cracks into their skulls, uncovering their motivations and making them real. Through Vowell’s hands, history stands up and lurches around, but it never quite manages to draw a breath.

Sarah Vowell reads at the Neptune tonight. Tickets are $43.50.