Pippa Middleton, the younger sister of Kate Middleton, Britain's Duchess of Cambridge, says in a new book that she is astonished by the worldwide attention she has received since her sibling's marriage in April 2011 -- and particularly by the spotlight on her derrière following her appearance as maid of honor in a form-fitting white gown.

"It is a bit startling to achieve global recognition before the age of 30 on account of your sister, your brother-in-law [Prince William] and your bottom," she writes in her party-planning book "Celebrate," excerpts of which appeared in a 24-page supplement Sunday in the British newspaper the Daily Mail.

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"One day I might be able to make sense of this," she continued. "In the meantime I think it's fair to say that it has its upside and its downside. I certainly have opportunities many can only dream of -- but in most ways I'm a typical girl in her 20s trying to forge a career and represent herself in what can sometimes seem rather strange circumstances. I am by nature an optimist so I tend to concentrate on the advantages."

Middleton, 29, whose given name is Philippa, is a scion of her parents' highly successful party-supply company Party Pieces, for which she has been the online-newsletter editor. She also has been a part-time publicist with the London event planners Table Talk.

She reportedly received the equivalent of almost $640,000 for the book from publisher Michael Joseph.

"Celebrate" features recipes for home entertaining, and includes anecdotes of her and Kate Middleton's childhoods in the British village of Bucklebury.