The Blogalization Conspiracy: Marginalia and Glossae
"So, really, the experience of a reader confronted with a newspaper in modern standard Arabic is not so much analogous to our being confronted with a New York Times in Latin, as Prof. Haeri suggests. It's more like a speaker of any medieval Romance dialect being confronted with a song in Provencal, a language that came to have a special role as a sort of international lingua franca of poetry."
The experience is even more convoluted for the English speaker learning Arabic, who generally learns Modern Standard Arabic before learning any of the various spoken dialects. I had the unusual experience of learning the Moroccan dialect before being exposed to MSA in any formal sense.
One might just as well have made the comparison to the speaker of any medieval Romance dialect who wanted to read a book or correspond with someone who spoke a different dialect in the Middle Ages. In such cases, books and letters would almost certainly have been in Latin, which by that time was an acquired tongue for all its speakers.