Discarding the unreliable late evidence for the Library of Alexandria in the Hellenistic period, I establish a new history of libraries and books on more secure primary sources. Beginning in the second century BCE at various places across the eastern Mediterranean, rich, powerful men began to sponsor collections of books. These new public displays of aristocratic and royal munificence (euergetism) so transcended earlier holdings of books—which had been small, vocational, and private—that in an important sense they constitute the invention of the library. As political institutions, these libraries depended on a revaluation of books, treating them as valuable irrespective of their content, and in various domains people increasingly attended to books as formal objects. Romans accelerated the pace and scope of this biblio-political revolution and extended the revaluation of books, transformations which gave a deeply anachronistic imprint to the frequently cited late stories about Hellenistic libraries.