Once digitized, a page of words loses its fixity. It can change every time it’s refreshed on a screen. A book page turns into something like a Web page, able to be revised endlessly after its initial uploading. There’s no technological constraint on perpetual editing, and the cost of altering digital text is basically zero. As electronic books push paper ones aside, movable type seems fated to be replaced by movable text. That’s an attractive development in many ways. It makes it easy for writers to correct errors and update facts. Guidebooks will no longer send travelers to restaurants that have closed or to once charming inns that have turned into fleabags. The instructions in manuals will always be accurate. Reference books need never go out of date. Even literary authors will be tempted to keep their works fresh. Historians and biographers will be able to revise their narratives to account for recent events or newly discovered documents. Polemicists will be able to bolster their arguments with new evidence. Novelists will be able to scrub away the little anachronisms that can make even a recently published story feel dated.