Letters in Amor en tiempos de Colera acquire a diversity of meanings that depend entirely on the conditions under which the letter is read, opened, sent, or not sent.
The letters are the only conduit of communication between Fermina and Florentino. For 50 years, Florentino's obsession is expressed through the letters that he writes. He writes feverishly, which also represents a window into his psyche, one which is as extravagant as it is nearly histrionic. This type of flaw is typical of many of Marquez's characters.
Florentino Ariza wrote every night. Letter by letter, he had no mercy as he poisoned himself with the smoke from the palm oil lamps in the back room of the notions shop, and his letters became more discursive and more lunatic the more he tried to imitate his favorite poets from the Popular Library, which even at that time was approaching eighty volumes.
The letters show Florentino's state of mind, including his penchant for obsessive thoughts and desires.
In the case of Dr. Juvenal Urbino, the letters are symbolic of his own life. As his health deteriorates, so does his writing, and this is (like with Florentino), another window into the mind and soul of the character.
[Urbino] wrote a letter of feverish love to his wife and children, a letter of gratitude for his existence in which he revealed how much and with how much fervor he had loved life. It was a farewell of twenty heartrending pages in which the progress of the disease could be observed in the deteriorating script, and it was not necessary to know the writer to realize that he had signed his name with his last breath
In chapter 6, Fermina (who has never been much of a writer) uses one final letter as a way to expiate the anger she feels for her situation. It is a special moment for Fermina, who asserts her femininity, her rights as a woman, her emotions and her frustrations in a way that effectively empowered her for once.
She had put into it all the fury of which she was capable, her cruelest words, the most wounding, most unjust vilification, which still seemed minuscule to her in light of the enormity of the offense. It was the final act in a bitter exorcism through which she was attempting to come to terms with her new situation.
In many ways, letters are the most honest form of expression of the characters. Through them, they declare love, say goodbye, and even summon their personal demons. The letters are certainly the most cathartic way for the characters to deal with their own situations in life. Florentino even writes letters FOR lovers as a way to vicariously experience love in a different way.
As a whole, the letters are symbolic of the unspoken word; those things that never get to leave our hearts because they can only be expressed in the deep intimacy of the ancient practice of writing. To a Garcia Marquez fan, this is a way for the author to pay homage to the conduit that he has put on a pedestal over and over again. Marquez basically gives an ode to writing through this novel, and exposes the incredible importance, romance, and tradition that writing (namely letter writing) brings to the lives of many.