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There is a link to the catalog for the Little Brown and Company, it is rather a large PDF file (81.8 mb) but included in it are two snippets of interest.
The first is shown to the left, it is a general letter about future publishing, and includes this paragraph about S. -
"Our Fall 2013 list may well send you off the cliff. J.J. Abrams - one of our world's most creative, brilliant, and canny storytellers - leads the list with a collaborative novel with PEN Hemingway-nominate novellist Doug Dorst. It's a book that is so surprising we cannot reveal its contents. It's a story for J.J.'s millions of fans, a story for people who love books. I can promise that there is nothing in this book that will not surprise you."
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The only other real information on the page is that the book will be 352 pages long.