The actress roped in her famous pals, including Jude Law and Ben Stiller, to pose for photos wearing a "magical" headpiece for the tome in aid of the Golden Hat Foundation, which she set up to help her friend's autistic son Keli.
Winslet's mission came to a halt when she underwent a minor operation - but she refused to take doctors' advice and rest up, and instead headed out to a party in a bid to land former U.S. President Clinton for her book.
She tells Ladies' Home Journal, "You wouldn't believe some of the things I did to get that hat to people. Like, I gatecrashed a private function to get the hat to Bill Clinton.
"It was a dinner party of about 30 people, and my friend foolishly gave me a ticket. I'd just had minor surgery and I had stitches, and I was like, 'I don't care, I need Bill Clinton, f**k it.' So I hobbled in to this party in my cocktail dress, and begged. Unfortunately he was surrounded by handlers who wouldn't let him put it on. But I needed to try. And most of the time it was fine.
"A lot of the time it was just me racing around the city to different events. Once my children and I made a road trip to watch Michael Phelps swim in Baltimore, so we could get him into the hat. I was terrified of losing it - and I was sure I'd lost it several times. See, at some point I want to auction it off to raise more money."
The book, entitled The Golden Hat, is set for release in April (12).