"It's a bad habit, " Ms. Feldman, 45, joked of the couple's book collecting.

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Or check out a book on book collecting.

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One side features the Genius of Medicine holding an open book in her lap, collecting water pouring out of a rock to quench the thirst of a sick girl beside her.

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Photographer Cunningham says the lone younger character is consistent with his experience in collecting images for the book.

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To dedicated fans of horology, the watch book is as much a part of collecting as the timepieces themselves.

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Now Facebook, Apple, Google and smaller app developers are collecting nuanced details like location data and address-book info, and across a wider breadth of people (more than a billion in the case of Facebook).

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