Chris O'Dowd and his Moone Boy co-creator, Nick Vincent Murphy, have agreed a six-figure deal to write two children's books based on their award-winning Sky series.
The first book is due out next autumn from publisher Macmillan, with illustrations by Irish company Cartoon Saloon.
O'Dowd and Murphy said: "Throughout the first three series of Moone Boy, it's often occurred to us that there's so much more we could do with the world of the imaginary friends, but the hassle of having to film things with our big clumsy cameras made it tricky to delve too much into it in the show."
They continued: "However, this feels like the perfect world in which to explore novels for a younger audience, with plenty of opportunities for fun doodles and illustrations by Cartoon Saloon.
"There will be lots of jokes and we hope that parents will want to steal the books from their children to read them too."
Macmillan's Venetia Gosling said: "I loved the first Moone Boy TV series and saw immediately how well the characters and scenarios could work in book form.
"Chris and Nick's writing is so warm and funny, with such a strong sense of family and community, that I know these stories will hold huge appeal for all ages and I'm very excited to be part of the team introducing Moone Boy to readers both here and abroad."