When people buy an item from someone on Poshmark, the seller gets a shipping label they print and use to send the item.

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The book appeared on several best-seller lists and has sold more than 100, 000 copies in both print and digital form in the U.S., according to Random House Inc.

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That sensibility led Topkis to her first winner, a 1995 British detective story called Death in the Garden, by Elizabeth Ironside. (In January Garden briefly beat out The Da Vinci Code as the top mystery seller on Amazon.com.) To publish this out-of-print title, Topkis had to track down the book's rights.

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