The Myth of Sisyphus, an essay about life's absurdity by Albert Camus, because his already annotated copy of it was left behind at work...and, alas, lost.
As I understand Wikipedia's interpretation of Camus on this topic, Ben should have no real hope of changing his lot in life, even if he keeps losing his book, but he is allowed to contentedly accept that fate. Hope would make him absurdly Kafkaesque.
Which reminds me of Sarah's wonderful description of a certain rare technology book's cover as Copernicus-esque. Alas, that did not help our customer who was searching for a book on Copernicus.
And I am making another Sisyphusian stack of books to read, including The Secret of Lost Things, by Sheridan Hay, a "charming novel about the eccentricities and passions of booksellers and collectors," as the front flap tells me, a gift from Sarah. Along with a beautiful holiday basket. "I was feeling crafty," she said.