The trope of “books as friends” has a long history in the Western tradition, appearing in the writings of figures such as Francesco Petrarch, Niccolò Machiavelli, W. E. B. Du Bois, and Virginia Woolf. The earliest clear articulation of the metaphor, however, appears in the letters of the Roman orator, politician, and philosopher Cicero. In the first letter to Varro in Familiares Book 9, written after his return to Rome following Pharsalus, Cicero remarks that he has been “restored to the favor of [his] old friends, that is to say [his] books” (Fam. 9.1.2 = SB 175: scito enim me, postea quam in urbem venerim, redisse cum veteribus amicis, id est cum libris nostris, in gratiam). This paper collects and analyzes references to books as companions, sources of consolation, and sites of affection in Cicero’s works, with particular attention to the letters and treatises from the period of his philosophical retirement, and shows how Cicero’s understanding of his personal relationships with old books was shaped by—and in turn shaped—his philosophical project. Tracing this metaphor from Cicero to later readers invites reflection on what it means to read old books today, how we make connections with others by sharing texts in common, and what we can learn about both past and future when we understand reading as an act of friendship.