Books like The Philadelphia Adventure

Vesper Holly has foiled murderers, crossed mountains, and narrowly escaped earthquakes. Now she's home in Philadelphia, where she can relax-until President Ulysses S. Grant asks for her help. The Centennial Exposition of 1876 is about to begin, and luminaries from around the world will be there. But so will Vesper's arch-nemesis, the evil Doctor Helvetius. There's only one person who can thwart his evil plans-Vesper Holly!