Even though Halloween may not be as big of a holiday extravaganza on Pippa Middleton's side of the pond, the royal sister-in-law is still "celebrating" the spookiest holiday of the year with the release of her new party-planning book, Celebrate: A Year of Festivities for Families and Friends, in London.

While the highly anticipated book doesn't hit stores in the U.S. until Tuesday, Pippa is making the rounds in the U.K., which included a stop at London's Daunt Books yesterday, where she hosted an arts-and-crafts event for a children's party.

Then the real fun with the grownups began, as Pippa changed into the evening wear of a Stella McCartney sleeveless black, gress and white dress and black pumps while she took posed for press photographs. "I feel incredibly lucky to be in this position to publish a book," she said.

And despite her British upbringing, Pippa has always had a soft spot for Halloween, too. "As a child, I felt that Halloween was a time when creatures of the night suddenly came to life – we would turn off all the lights in the house and let flickering candlelight conjure up scary shadows and imaginary figures lurking in dark corners. Nowadays, I frequently celebrate Halloween over a supper with friends," she told Parade. "It's a wonderful excuse to let your imagination run riot with gory-looking food and special effects."

Some have suggested, however, that when it comes to Halloween, Pippa might need some help in the imagination department. Halloween activities that Celebrate suggests: Stir witchy cauldrons of pumpkin soup; hang homemade spiders inside window nooks; string cobwebs on tables; and haunt gardens, attics, and stairways with ghosts made from sheets.”

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