While not strictly applications, some ebooks are so interactive and full of enhanced content that they're just as valid for an App of the Day as any dedicated software. After all, the superb interactive Alice in Wonderland may be classified as an app, but it's as good a children's book as anything offered on Kindle or iBooks. 

And it is the latter of those ebook applications that we turn to as the host for today's App of the Day, the superb, and now free...

Yellow Submarine

iPad, iPhone, iPod touch (through iBooks)

Based on what is technically a kids' picture book released in 2004, the interactive version of The Yellow Submarine adds so many extra features that it's an entirely different proposition. The art is the same, as are the words, however, almost every page has something that you can move, prod or play, with a few surprises along the way.

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Now, we're massive fans of The Beatles here at Pocket-lint Towers, and even have collectable figures of all of the members in their Yellow Submarine form, so this ebook was always going to be a favourite. But, we've even overheard others comment on how cool it is, and kids will love it even if they've never even heard of the band.

As well as the ability to touch items in the scenery, provoking animations or audio clips, spattered throughout the book are video clips from the movie which play important scenes. Plus, you can choose to have the entire book read aloud by Dean Lennox Kelly (ex of Channel 4's Shameless, among many other TV shows). You can even touch specific words and phrases and jump through his narration. Other, bold words will plau audio files, such as the noise a character makes or a snippet from a song. Naturally, everytime you touch the words "Yellow Submarine" you hear the chorus of the eponymous track.

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There are 44 pages in total, with the last couple dedicated to flogging you the soundtrack through iTunes. But hey, Apple is currently offering up the book completely for free at the moment, and there's no other advertising or sponsorship throughout the main body of the ebook. We can live with a few links at the end.

In fact, we would happily live with sponsored stuff in the middle, if that's what it would take. The Yellow Submarine interactive ebook is a godsend to fans of the band, the movie and the iconography. Yeah, The Beatles didn't actually do their own voices (with Twiggy from The Royle Family lending his as Paul) in the original film, but it's a wonderful, trippy experience that young and old can enjoy equally.

It certainly holds pride of place on our iDevices. Now, excuse us while we go and play with our Blue Meanies.