Mind Candy, developer of Moshi Monsters, has signed its first major licensing deal. The deal gives Penguin Group the rights to publish a series of books based on the Moshi Monsters property.

Moshi Monsters is a free-to-play online game that allows children around the world to adopt their own pet monster, play games, customize their homes, explore the virtual world, and solve educational puzzles. More than 20 million players have registered to date on the website.

The first book to be published by Penguin will explore Moshlings––the cute, colorful, and collectible pet creatures of the Moshi Monsters. The book will tell the Moshlings’ backstory, habitats, quirks, and more. The book will also contain a unique code to unlock a secret Moshling at the Moshi Monsters website.

Two books are planned for release this year globally, and five more will follow next year.