Of the many institutions suffering through the world’s metamorphosis from analog to digital (real to virtual, offline to online), few are as beleaguered as that bedrock of our culture, the public library. Budgets are being slashed by state and local governments. Even the best libraries are cutting staff and hours. Their information desks are seemingly superseded by Google, their encyclopedias are gathering dust. And their defining product, the one that lines their shelves, now arrives in the form of a weightless doppelgänger that doesn’t require shelves.