We've seen this sort of thing before: People who offer to publish your tweets in a book, companies that publish Wikipedia articles, and so on. They never really seem to catch on, but people just keep trying. This is from Laura Hazard Owen at PaidContent:

Saving something to read later, in Instapaper or Pocket, doesn’t mean that you’ll ever actually get around to reading it. A company called Blackstrap aims to fix that: It will print all of your read-later articles into a $15 book. “If an article deserves a little time, then Blackstrap it: choose the ones you want to linger over and we’ll print, bind and send them to you, to enjoy undistracted,” the company says.

The "books" can only be up to seventy-five pages long. Blackstrap says they've figured out the copyright issues: "You can only print an article from a given URL once, and the company’s terms and conditions specify that users can’t make copies of their books." The books can take up to a little over two weeks to arrive in the mail. This sounds like a totally sustainable model.