I feel lucky that my daughter is a voracious reader, but her curiosity has a downside: She always wants to know more. So I also feel fortunate to have discovered Duh! books.

These fiction e-books, geared toward kids from second to fifth grade, are an awesome interactive resource on a variety of kid-friendly topics. From the universe and volcanoes to horses, cats, knights and castles, the growing Duh! collection is full of great information, simple explanations, cool interactive graphics, and links to learn more.

Be aware that Duh! books are created by school textbook writers from the Netherlands, which means that the information is correct, but the translations can differ from American English. For example, temperatures are given in Celsius, and while the height of Mount St. Helens is given in feet, it’s 10.000 feet (instead of 10,000 feet with a comma, as we would write it). I also wish that they’d described groups of stars as constellations, instead of as signs of the zodiac.

That said, they’re a fun resource for kids eager to learn more. I love that we can carry several Duh! books on our iPad (which comes along on pretty much every road trip we take anyway) so there’s always something cool for my daughter to read. In fact, I wouldn’t be surprised if she opted for a Duh! book over a zillionth round of Tiny Wings.

Duh! books are $3.99 each on iTunes and require iBooks. They also work on Mac laptops or your desktop, but the interactive features are best experienced with the touch screen of an iPad.