Together, they have made this weekend one of the most sensational in publishing history. With millions of advance orders for each of their books and multiple print runs already planned, Madonna and David Beckham have challenged the widely held belief that celebrity writers don't make a profit.
Now publishers are drawing up wish-lists of the stars they would like to sign up next in an effort to replicate the "Madge and Becks factor". Bill Clinton, Sir Elton John and Alastair Campbell are among the handful of figures believed to have the necessary international appeal.
Though wildly different in nature, both Madonna's children's picture book, The English Roses, and Beckham's ghost-written autobiography, David Beckham: My Side, look certain to ride high in the bestseller charts for months. In a bullish show of confidence, their publishers, Penguin and HarperCollins respectively, paid the stars seven-figure advances and ordered initial print runs of more than a million apiece.
It appears to have paid off. Madonna's children's book, though not even published until tomorrow, is already into its third print run.
Meanwhile, buoyed by its recent serialisation in The Sun and The News of the World, My Side is also having to be hastily reprinted. As a satisfied-looking Beckham clasped a copy at its official launch in Madrid on Friday, queues were already forming at bookstores in cities from London to Tokyo - where he and his wife, Victoria, are idolised.
The phenomenal success of the two titles appears to give the lie, once and for all, to the notion that celebrity books don't sell in their own right.
Only last year, the celebrity autobiography was being roundly written off as a lost cause by the trade press. Scandalous revelations in the memoirs of former Conservative minister Edwina Currie and television presenter Ulrika Jonsson translated into huge sales for the newspapers that serialised them, but the books themselves failed to set the world alight.
To Michael Doggart, publishing director at HarperCollins, the reasons why some celebrities sell and others don't are simple.
Beckham and Madonna are guaranteed to shift copies, he says, because both have international profiles and are widely seen as role models.
"The thing about Beckham is that you have so many potential markets in which he can sell," Mr Doggart said. "You've got the newspaper serialisation and a major market in Japan, where he and Victoria are adored."
For Helen Fraser, managing director of Penguin, the qualities of Madonna's book, inspired by the Hebrew Kabbalah philosophy, were distinct from those of most star-penned titles. She insists the megastar won her over with the strength of her writing and imagination.
"We knew they were stories by Madonna, but we bought them because we thought they were good," she said.
* The Independent on Sunday's literary editor, Suzi Feay, gives her assessment: On David Beckham: My Side, she says: "In the end, the book's about a man who has a supernatural talent for kicking a ball and a woman who has a supernatural talent for wearing a basque. It's one of the charms of this book that after reading it, you can't help but think: God bless 'em."
On the spiritual flavour of The English Roses: "In her latest venture, Madonna is smart enough to align herself alongside WB Yeats, Zadie Smith and Borges, three writers who have found inspiration in this mystical - and fiendishly hard to comprehend - doctrine."
Publishers' VIP dream team
Sir Elton John
Why he's so hot: Has had a colourful career and personal life for 30 years.
What we'd like to read: The truth about his marriage and his spending sprees.
What we'd be likely to read: His celebrity chums and celebrity fancy dress parties.
Why he's so hot: At 41, he's still one of Hollywood's most bankable idols.
What we'd like to read: His marriage to Kidman, his fling with Cruz.
What we'd be likely to read: How Scientology saved his life, and how he has no insecurities about his height.
Why he's so hot: Still one of the world's most popular public figures.
What we'd like to read: About when Hillary nearly left, and Monica Lewinsky.
What we'd be likely to read: His unbending admiration for Tony Blair, his undying love for Hillary.
Why he's so hot: The row with the BBC has given him a huge profile.
What we'd like to read: What he really thinks about Tony Blair and Cherie.
What we'd be likely to read: He's a pussycat (at heart), he's a socialist (at heart).
Why he's so hot: His bizarre private life makes for compulsive gossip.
What we'd like to read: About his marriages, those allegations and that face.
What we'd be likely to read: About skin disease and being deeply misunderstood.