It's the first of four and will be out in September.

Grammy Award-winning musician Pharrell Williams is set to release a new picture book in September – the first of four books he's planning for young readers.

Due out Sept 22, Williams's first book is inspired by his hit song Happy and will feature photos of “children across cultures celebrating what it means to be happy.”

Putnam Books for Young Readers, an imprint of Penguin Young Readers, will publish the book with a first printing of 250,000.

“I'm humbled by the global success of Happy, but especially in awe of the song's young fans,” says Williams. “My collaboration with Penguin allows me to continue a dialogue with these children in a fresh, new way. We're both committed to feeding the curiosity of young minds with imagination.”

The singer, rapper, songwriter and producer has been broadening his scope in recent years, appearing as a coach on TV talent show The Voice, partnering with Adidas and Uniqlo on fashion collaborations, concocting macaron flavours for Parisian brand Laduree and curating an exhibition at Toronto's Design Exchange Museum.

Last April, he wrote a “social book” called Inspiration that was published online, with its words erased for fans to guess.

Happy was one of 2014's most ubiquitous tracks, earning Williams a Grammy for Best Pop Solo Performance and becoming the best-selling song of the year in the US and Britain. It was also on the soundtrack of the animated movie, Despicable Me 2. – AFP Relaxnews