Pippa Middleton, sister of Prince William's wife Catherine, has been unceremoniously dumped by British literary agent David Goodwin, who masterminded an extraordinary US$640,000 advance on her first book. "I am very sorry it has happened, but yes, it is true: I no longer represent Pippa and I wish her every good luck," Goodwin told the Daily Mail . Why is the sister of the Duchess of Cambridge no longer worthy of Goodwin's attention? For starters, they were an odd couple. Goodwin's clients tend to be literary heavyweights, not newly minted royal celebrities - his stable includes biographer Claire Tomalin, novelist Vikram Seth, and historian William Dalrymple. And while Goodwin secured a massive advance for Middleton, sales of Celebrate: A Year of British Festivities for Families and Friends were a flop. Was that poor management of the marketing or just a lousy product? Middleton was severely criticised in the British press for simply cashing in on her fame and offering simplistic recipes and party ideas. Apparently, it takes more than a famous name to sell a book. Middleton's days as a writer are not over yet, however. She will soon have a monthly column in a British supermarket chain's magazine, Waitrose Kitchen . The column, comprising cooking and party-planning tips, will be called "Pippa's Friday Night Feasts".