Sarah Vowell has made a career of putting herself front and center, her personality the lens through which an audience views her generally thoughtful, well-researched essays and radio pieces, regardless of topic. Intelligent and well-schooled in all sorts of liberal arts arcana, Vowell punctuates her pop-culture safaris with enough insight to justify the often self-involved cul-de-sacs her approach inevitably generates. But in recent years she’s drifted from considerations of the meaning of Frank Sinatra into examinations of watershed moments in American history, such as the genocidal deportation of the Trail of Tears, and when foregrounding herself in these forays, Vowell tends to occlude as much as she illuminates. When the subject is 40 pivotal years of American history, the whole shtick may be more distraction than it’s worth.

In her new book, Assassination Vacation, Vowell leads readers on a virtual tour of the murders of three late-19th-century presidents: William McKinley, James A. Garfield, and, of course, Abraham Lincoln. Strapping the narrative to an exhaustive physical exploration of sites associated with the murders–from Ford’s Theatre to the seaside Jersey town where Garfield went to die to the Adirondack rail depot where vice president Theodore Roosevelt learned of McKinley’s death–she gradually develops her canny thesis, which maps the excesses of the Gilded Age, its nascent imperialism in particular, onto the capital-stoked interventionism of our own day. While owning up to some sympathy for the assassins given the current oval occupant, Vowell sees a stronger kinship between the killers and their victims. “The egomania required to be a president or a presidential assassin makes the two types brothers of sorts,” she writes. “The assassins and presidents invite the same basic question: Just who do you think you are?” The comparison is valid if old hat–noted historian Peter Gabriel, for one, made it in 1980 in “Family Snapshot”–and the question is a good one, though one might very well ask it of the author herself.

It’s not that Vowell, or her endless supply of articulate friends–many doubling as chauffeurs–don’t have a lot of interesting things to say. Or that some of their facts are a little fuzzier than you’d hope (the dates on one incidental sketch, of the doomed Spanish king “El Hechizado,” are only off by, oh, 100 years or so). It’s that the history itself is more interesting, and you’re constantly being pulled out of it by Vowell’s tangents, some of which work but many of which don’t. When describing the not-so-famous pocket contents of the deceased John Wilkes Booth, for example, she reasonably enough introduces them by way of the rather-more-famous contents of the martyred Abe’s. Why it’s necessary to also enumerate the contents of her own is less clear. The comparison feels phony and forced, and while I can see how it might make her experience more meaningful, it didn’t do much for mine.

Almost half of Assassination Vacation is devoted to Lincoln, but these pages are its dullest. The relative familiarity of the tale, combined with Vowell’s conspicuously unexamined idealization of our greatest president, seems mostly to blame–a lot of the neat-o factoids she’s got in her arsenal are actually fairly well-known, and she’s in high dither mode to boot. But her treatment of the conspirators’ thrilling attempt on the life of secretary of state William Seward, which happened at the same time as the murder that overshadowed it, is riveting, and a long digression on the secretary’s much-maligned purchase of the Alaska territory beautifully showcases the strengths of her meandering stock-in-trade. Similarly, her resoundingly first-person account of her visit to the Dry Tortugas, site of the island prison where the infamous Dr. Samuel Mudd, the copperhead physician who set Booth’s leg when he was on the lam, did time, creates an eerie sense of place that traditional scholarship would be hard-pressed to deliver. But all too often these spells are broken by drab excursions into the purely personal: Vowell’s mixed feelings about her early American pedigree, which, it turns out, includes a murderous, proslavery thug. The contents of her purse and the inconvenience of post-9/11 flight. The antics of her three-year-old nephew. And so on.

By the time you get to dead president number two, Garfield, you’re fervently hoping Vowell has run out of asides as well as Lincolniana, a wish that’s temporarily granted. Faced with extracting a story from the byzantine politicking surrounding Garfield’s election and execution, she’s got little choice but to stick to the facts. A compromise candidate within the Republican party, Garfield and his short presidency arose from the complicated intersection of northern triumphalism, New York-style corruption, and the fading of the reconstruction. But Vowell’s recounting of the deals and double crosses–and their bearing on assassin Charles Guiteau’s motives–is the most lucid, arresting section of the book. The utterly forgotten Garfield gets his due, painted in shades more wistful and noble than you’d ever guess, and, as with the Seward sequence, Vowell’s handling of the material–in this case, the trial of the crazy-as-a-loon Guiteau–is perfectly measured. Though she still indulges in some side trips, like the ponderous backstory of the upstate cult Guiteau once associated with, the narrative is better served by them here than elsewhere.

But then, flush with momentum, Vowell moves on to McKinley. Cashing in her structural chips, she doesn’t bother to flesh out the president himself, focusing instead on the historical significance of the site of his assassination, Buffalo’s Pan-American Exposition of 1901, and the ensuing succession of a certain Rough Rider to the suddenly vacant throne. The longer focus reflects a sneaky corollary theme–there would be no more Lincolns; the march of American history began to transcend the individual at precisely this point. But Vowell’s mostly interested in the McKinley era as a flat-out metaphor for the modern American imperialism whose dawn it coincided with.

At first, and especially in her symbolic decoding of the exposition’s frighteningly familiar globalist rhetoric and iconography, Vowell maintains the relative objectivity of the preceding chapter. There are fewer laughs from here on in, and rightly so: tying all manner of present-day national dysfunctions to their turn-of-the-century roots–the Dixification of the GOP, the cynical waging of third-world wars for political gain, the bottomless expansionist hunger that’s haunted the U.S. ever since we messed with Texas–is no mean feat, nor likely to be very uplifting. So begrudging the turn she takes for the dead serious here seems a little petty. But somewhere in the fever pitch of her dismay, she gets lost.

Maybe it has something to do with the way Roosevelt, through sheer force of personality, damn near crowds McKinley out of the chapter, an appropriate development given that he did the same thing in real life. In any event TR’s big entrance, which caps all the background material on unrest at home and the Spanish-American War abroad, seems to shove this history aside more than sum it up. And following a muted acknowledgment of the degree to which Teddy’s legacy doesn’t quite jibe with her sins-of-the-fathers thesis, Vowell retreats to the consideration of her navel, and the proclamation of her personal convictions.

It’s hard to disagree with most of them–at least if you’re left of center politically–but the ferocious finality with which they’re expressed grows wearying, and they eventually fall into the no-man’s-land between preaching to the converted and sneering at the unwashed. In one revealing anecdote, Vowell recounts her seething reply to a fellow traveler’s innocent remark about living through the “historic” east-coast blackout of 2003: “Sir, except for the people who were there that one day they discovered the polio vaccine, history is rarely a good idea. History is one war after another with a bunch of murders and natural disasters in between.”

Now, I can only guess how someone who’s never considered that history might be a nightmare from which we’re trying to awake would take that kind of self-righteous condescension–but I can tell you how someone who has did. And in the context of various other self-congratulations and finger-pointings, such pronouncements are reminiscent of the better-than-you elitist media bugaboo the right so loves to trot out, and that the left seems all too happy to play into.

Something faintly smug and more than a little precious lurks behind Vowell’s sincere championing of the skeptical, secular patriotism that seems sadly to have vanished from most political discourse. And while a good deal of it may spring from an anger and despair that’s all too understandable, some of it seems the habitual self-regard of someone who can’t help reminding you that she used to be a rock critic and has a master’s degree in art history. Or who lists blizzards of facts that primarily demonstrate how charmingly, obsessively self-educated she is. Or who describes herself, in her bio, as “a McSweeney’s person.” On a tour with someone like that, you feel pretty irrelevant to the process before long–maybe because the guide’s head keeps blocking out the informative plaques along the way.