An excerpt from Stross’s new book, which goes inside Y Combinator, Paul Graham’s Silicon Valley startup incubator:

“The Kalvins are attempting an improbable thing, making a case for a nondigital product: ‘Having a physical product that you flip through and have on your coffee table and show your friends—it’s real­ly valuable! We’ve actually bought photo books for our friends and family. It sucks because you have to spend hours making them, finding the photos.’ Every dorm has to prepare one each year, pay a printer $20 a copy, and buy at least a hundred.

“Graham returns to his still-unanswered question: ‘Where does this expand?’

“A Kalvin suggests offering a book based on your personal calendar and Foursquare check-ins. Or your tweets for the year.

“‘You’re not serious, that people are going to print up tweets from last year?’ asks Trevor Blackwell, who is in his early 40s, about the same age as the other three founding partners. He too has a day job, as the chief executive of Anybots, the robot company that then shared its building with Y.C.

“‘Actually, I have a tweet book,’ says one of the Kalvins.”