E-books are already a fraught subject for many readers, writers, publishers and designers, but children’s e-books are even more so. Is it rotting their minds? Is it as good as good ol’ paper? Is it too interactive for their own good? Obviously there are no practical answers to such questions, but at least one children’s e-book/app/thingie (what do we call these things, again?) is doing it very, very right. It’s called “The Fantastic Flying Books of Mr. Morris Lessmore,” and it’s like a well-written bedtime story and an immersive animated movie at once — without being “too much” of either.

Every page has some delightful, hidden feature embedded into it.

Part of why the book works so well is its top-shelf creative pedigree: author William Joyce is also an accomplished illustrator and animator who’s published New Yorker covers, won a bunch of Emmys, created character designs for some of Pixar’s first animated classics, and worked on many others for Dreamworks and Disney. With his cohorts at Moonbot Studios, he created an interactive book-app around the story and a standalone animated film–so you can experience “The Fantastic Flying Books of Mr. Morris Lessmore” however you like.

Designing interactive interfaces for kids is no mean feat, and the Moonbot team really made some great choices with “Morris Lessmore.” When you open up the app, it doesn’t waste your time with teaching-screens about how to interact with it–it just smoothly enters the story. (A key feature, I imagine, when you want to get Junior to go the youknowwhat to sleep ASAP.) Gently animated cues surface in the lush visuals at just the right time, encouraging you to explore the app rather than slavishly plod through it: When a house gets picked up in a tornado, you can use your fingers to swipe and spin it around–but you don’t have to.

In fact, the interface design is so subtle it wasn’t until I was about six pages in that I realized that every page of the app has some delightful feature embedded into it that you have to find for yourself. This is the key to a successful children’s book–inviting them to play and explore and be curious, not just jab buttons to activate cheesy visual effects. And mercifully, every gewgaw in the book has a button so you can toggle it on or off: For example, you can kill the voiceover so you can read to your kid in your own voice the way God intended, or silence the music and sound effects if you want to. But they’re all just a tap away if you change your mind–and the whole experience is so well-produced, you very well just might.

[Buy “The Fantastic Flying Books of Mr. Morris Lessmore” in the iTunes App Store for $4.99]