If you've been following Sarah Vowell--writer, radio persona, late night talk-show guest, superhero voice actor--for a few years, you might have noticed a bit more stealth in her public stride of late. The success of her last two books, Take the Cannoli and The Partly Cloudy Patriot, her unlikely (which is to say glorious) involvement in The Incredibles, and her visibility as a semi-regular guest on late-night talk shows all lend the sense of a star on the rise. Because the world of rising stars needs more Sarah Vowells, this development is excellent news. It also raises questions about the way her authorial persona, which has always been about the interests and obsessions of an outsider, a nerd who makes no pretense to be otherwise, might evolve in light of her increasing popularity. A few indications can be found in her new book, a digressive travelogue in which Vowell measures out her fascination with the macabre elements of American history by making holiday destinations out of the assassinations of Presidents Lincoln, Garfield, and McKinley. Good times.

With the possible exceptions of her family and The Godfather, Vowell's most fruitful recurring subject has been political history. Thanks to an effortlessly colloquial tone, she approaches these subjects as a fan; she's a buff, as opposed to a scholar. That's not to say the book isn't learned; she has clearly done a lot of homework. But she's also smart enough to present her arcane knowledge conversationally. Vowell addresses her historical passions the way a record collector addresses rock lore: with the understanding that it's obviously of critical importance not only to have a position on, say, the likely culpability of Dr. Samuel Mudd in the conspiracy to assassinate Lincoln (Vowell votes yes), but to go and see his house--where John Wilkes Booth rode, with a broken leg, in the middle of the night, immediately after shooting the president--and even his prison cell, on a remote island off the Florida coast. Vowell's connection to such obscure fistulas of the American experiment is enthusiastic and compelling. Vacation is never better than when, inspired by the sheer availability of knowledge that few of her peers would ever even think of thinking of, she leaps on the boat that will take her where the facts are (like when she visits Mudd's watery prison and she becomes seasick and vomits en route).

Armed with such tidbits, she turns her sights on the present-tense history we're all in the business of writing. Her preferences are clear ("I like to call [George W. Bush] 'the current president' because it's a hopeful phrase, implying that his administration is only temporary"), but her curiosity is endless, and the cleverly nonacademic style of inquiry goes a great distance toward making history--past and present--an accessible interest.

Compare Assassination Vacation, with its left-turn anecdotes about her long-suffering travel companions, and wry observations (the "boardinghouse where John Wilkes Booth and his coconspirators gathered to plot Lincoln's death is now a Chinese restaurant called Wok & Roll") to Michael W. Kauffman's recent study of Booth, American Brutus. The latter represents a lifetime of heavy scholarship, and is intent on presenting the authoritative case against Booth "as it developed in 1865." Impressive and authoritative though it is, Brutus bogs down in obsessive literalism--to a layperson, its narrative becomes a blur of contradictory and superfluous facts. In many ways, Vowell's lighter fare trumps Kauffman's erudition, if only because her book is more pleasing. The most important teachers, after all, are the ones who discover a way to make the material relevant to their students.

The book falters when you get the sense Vowell is trying too hard to sell her premise; there are a few too many instances at which she steps in to remind us that her morbid proclivities are adorably weird. However, themes like history, politics, and patriotism are too big to be understood without some refractive personalization, and few contemporary nonfiction authors are equipped with a voice as distinct as Vowell's. You can almost hear her speaking every line.