Pippa Middleton begins the introduction to Celebrate, her new collection of home entertaining tips, by saying she is "by nature an optimist". Which ought to come in useful, given the book has only sold around 2000 copies in its first week.
This comes in spite of a 50 per cent discount on the cover price, and a considerable publicity campaign by Penguin, which paid a reported £400,000 ($776,000) advance to publish Pippa's poorly received tome.
So far, that's about £200 per copy sold.
As a celebrity publishing flop, Middleton is in illustrious company. Julian Assange was supposedly paid £500,000 for his memoirs, which sold just 644 copies in its first weekend.
Arnold Schwarzenneger's stellar career and scandalous personal life could shift no more than 27,000 copies of his autobiography Total Recall in the month after its publication. He reportedly received a seven-figure advance.
In 2006, Wayne Rooney agreed to write five books over 12 years for HarperCollins. His advance was £5 million. The second book sold just 6000 copies in six weeks.
If she never earns any further royalties on the book, Middleton can still comfort herself with that £400,000 advance.
The picture is less pretty for Penguin. Depending on formats and discounts, a publisher that spends half a million pounds on a book might have to sell three times that many copies to justify its magnanimity.
Editors at major publishing houses have the budget and power to make offers of up to six figures. But a six-figure advance such as Middleton's would likely be signed off by the head of the Penguin division responsible.
Anything larger than that - Tom Wolfe's US$7 million ($8.6 million) for his new novel, Back to Blood; Keith Richards' US$7 million for his memoir, Life - would go straight to the very top.
"There's a lot of pressure on editors to buy celebrity titles ... to corner the Christmas market," Tom Tivnan, features editor of The Bookseller, explains.
"You often see some panic buying of B- and C-list celebrity memoirs. A lot don't make their money back."