Book publisher Penguin has acquired worldwide publishing rights for books based on ustwo’s mobile game Whale Trail, the companies have announced at the Bologna book fair.

Whale Trail is available on iOS and Android, and bagged plenty of critical acclaim after its release. ustwo co-founder Mills has talked candidly about the game’s need to sell 300k downloads to make back its development costs – a milestone which it hasn’t yet hit.

The Penguin deal – inked for its Puffin subsidiary – may help. A digital picture book will be released in October 2012 starring the game’s main character Willow the Whale, with other digital AND physical books to follow in 2013. ustwo will be working with Penguin on the narrative for the books. Willow joins fellow digital brands Moshi Monsters and Skylanders in Penguin’s stable of licences.

“I discovered Whale Trail from Gruff Rhys’ music video. When I downloaded the app, I was hooked. There’s something so fresh and cool about the art direction,” says Penguin’s Eric Huang in a statement.

“I wanted to know more about Willow and his world and thought, we should publish a book. And since Whale Trail is a digital brand, it made sense to lead with an e-book.”

Mills is understandably chuffed with the potential for the partnership. “Penguin genuinely and passionately share our enthusiasm for developing the brand further, and the coming together of the traditional publishing powerhouse and our first game IP, is a match made in heaven.”

Next up, plush toys? It worked for Angry Birds…