She has signed a deal with Orion Publishing Group-owned Spring, which picked up Newton’s first book How the fudge do you garden?
The book followed her popular blog with the same name and will be released early next year.
At Sunshine, she led the creative output and the BBC Three online transition campaign. She has also helped the agency pick up business from ghd, Street Feast and the London Philharmonic Orchestra.
Newton has also worked at Wieden & Kennedy and SapientNitro.
The agency's co-founder and chief creative officer, Al MacCuish, said: "Hollie represents the next generation of creative polymath.
"She’s talent, pure and simple. She has an astonishingly versatile skillset and range of interests – and the drive to go with it.
"I feel like we’ve had a young Jamie Oliver passing through. Given the subject matter of her book, it proves – as if proof were needed – that Hollie really is a force of nature."