Fans of Aristotle and Dante Discover the History of the Universe (YA Saenz, Benjamin) will enjoy the Go SkyWatch Planetarium Guide for iPhone, iPod Touch, and iPad or Google Sky Map for Android devices. Both use GPS locators to generate a map of the sky with a guide to all the planets and stars, complete with interesting information. It's the perfect app to take outside for some stargazing, just like Aristotle and Dante loved to do.
If you loved Across the Universe (YA Revis, Beth), explore the universe with Solar Walk for iPhone, iPod touch, or iPad; or try Solar Planets 3D for Android devices. Both apps are tours of our solar system that allow users to zoom in on planets while learning the history of space exploration. Who says you need a spaceship to navigate through space and time?
If games are more your style, there are plenty of apps perfect for fans of popular books. Readers who can't get enough of vampires and zombies and loved The Immortal Rules (YA Kagawa, Julie) will enjoy Infect Them All: Vampires for iPhone, iPod Touch, and iPad. Beware: it's addictive.
If you can't find the perfect app to complement your favorite book, you can create your own with Yapp, which allows users to make apps for free without any coding or technical skills.