I'm not sure if you're talking about the city of Rome here or the Roman Empire in general, Valeriana. Are you talking about Roman citizens or all subjects of the empire?
At any given time during the height of the Roman empire, it had an estimated population of about 50 million people. These would not only include Roman citizens but anyone within the realm of the empire, from Hadrian's Wall to the Arabian peninsula. The city of Rome itself had an estimated population of 1 million, of which as many as 500,000 were said to be slaves, most of them owned by the 600 or so Roman senators. During the reign of Augustus, who ruled from 27 BC until 14 AD, and based on his own census, there were somewhere between 4 and 5 million Roman citizens (both men and women) within his empire, which was roughly about 10 percent of the entire population of the Roman Empire.
So when you're talking about this high literacy rate that supposedly existed, you're obviously not talking about the non-citizens, are you?
When you're talking about books, you're obviously not talking about books in the modern sense: printed words bound into an easily kept compilation of pages. Back then, "books" were papyrus scrolls that were often "bound" (or collected) in a bucket for easier carrying and storage. Papyrus, depending on its quality, was very expensive, so right there access to "books" was limited as not everyone could afford one.
As far as signing one's name goes: that doesn't support any kind of literacy because, as is even the case still today, oftentimes a simple "X" was sufficient.And for the innkeeper who was reading the Life of the emperor Hadrian ..., that's one innkeeper about whose history or pedigree we know nothing about.
Lugdunum (modern-day Lyon) was, as the capital of the Roman province Gallia Lugdunensis, the second most important city of the Roman empire for almost 300 years after its founding in 43 BC. Little surprise then that it would have "book sellers" and feature many other "modern" amenities.
Here's a population breakdown (based on a 65-million population):
http://www.unrv.com/empire/roman-population.phpBreaking down the 65 million population estimate, some additional assumptions can be made:
* 500,000 soldiers (legionaries totalling 150,000 and auxilia making up the rest)
* Approximately 600 Senators made up the elite of the elite.
* Perhaps up to 30,000 men filled the roles of Equestrians (knights), or the second tier of the aristocracy.
* 10 to 30% or 6 million to 19 million people lived in the cities, leaving the vast majority of some 46 to 59 million people to live in the country as independent and mostly tenant farmers.
* Rome itself was made up of over 1 million people and, though it would shrink remarkably after the fall of the west, no city would surpass that number until the great urban population booms of the industrial age, 1,500 years or more later.
* The slave population of Rome approached 500,000 on its own, probably half of which were owned by the 600 men of the Senate. Additional estimates have suggested that of the total 65 million people, 2 to 10 million may have been slaves.