Letters and Letter-writing
Letters and books were written primarily on papyrus. Parchment was coming into vogue, but not as common. Initial drafts were written on wax tablets and then scribes and copyists transferred the text to papyrus. Books were written on scrolls or stitched between harder surfaces (wood, leather,) as a codex. The cost of materials and ability as well as the ability to read and write limited the access of this medium to the better educated, a relatively small percentage of the population.
Letters and books were carried by private couriers and the modes of travel would dictate the length of time it took to reach the intended recipient.
There was an official postal service, the cursus publicus, which was strictly a governmental post under the authority of the emperor or his designated agent. Private citizens were left to their own devices.
I recommend “It’s in the Post” by Pauline Allen (see Select Reading List and available online). She is both educational and entertaining—great anecdotes that bring this topic alive.