I read Assassination Vacation a few years ago, and loved it. Vowell's morbid sense of humor speaks to me. And really, who isn't fascinated by historical assassinations? What? Not many people? Just me? Never mind, then.
I enjoyed this series of politically-themed essays as well, although I was a tad put off by her sarcastic vitriol aimed at all things Republican. However, this book was written in December of 2001, in the wake of 9/11, so I think some opinions were slightly cloudy, no pun intended.
I think Sarah Vowell is basically Jon Stewart in female form. With a squeakier personality.