Letters to a Prisioner - Goikoetxea and Berger

Looking for materials to conceive a narrative structure I found very interesting the letters that prisoners receive. I took this real anecdote related to this activity:

A friend of mine, a 60 years old writer of the Basque Country called T.Goikoetxea, told me that he was sending some letter to a prisoner. He really knew the prisoner because they both have a lot of friends in common but they did not meet for several years.
Goikoetxea was sending letters with a pseudonym. He send the prisoner 51 letters. The writings were based on fictitious characters that belong to some of Goikoetxea's novels. These characters preferences, places, political activities, aesthetics and kind of language are very very familiar to the prisoner social environment but no one of the names are known for him. Each letter has a different content but some of the characters appear and disappear and it is possible to relate some plots between the letters.
According to some information that Goikoetxea knew from the prisoner lawyer, at the beginning, the prisoner thought that the letters were not for him. Letter after letter he started to identify in his imagination some of the characters with some of his friends, acquaintances and public persons, and he even made the genealogical tree of the characters, recreating the stories and filling the gaps with his imagination. After more than twenty letter he started to guess who could be the writer and finally he discovered him.
After receiving the 51 letter the prisoner was released. He knew that the jailers read the letter before delivering them so when he was leaving the jail, the prisoner told the jailers ironically: Oh, what a shame, you get rid of narratives!!! The novel has finished.

Using this anecdote I find very interesting the structure of a narrative in which a prisoner is receiving letter but never answer them, all what you know about the writer and the prisoner is from the letter. Just the way in which the prisoner imaging what is described is suggestive but if what is describe is space? How can be space interpreted through a narrative when you are locked in a claustrophobic minimal room and deprive of free space?

After this first discovery, I was looking for more material related to this kind of narratives. I fortunately found a novel of the British art crit, novelist and painter John Berger. Berger in his novel "From A to X" recreate a story in which I am interested. His novel is based on the letters a prisoner is receiving from his lover, a woman that send him letter about their love, his captivity, freedom... One of the most interesting part are the description of her everyday life in detail that allows the prisoner to go out of the cell and get in her bedroom with each letter. The letters have not date so the order is not established and this way, as in Perec's Life: a user's manual, the time is not responsible for telling the story.