You can find the official French edition through Gallimard.
Camus and Casarès met in Paris on the same day as the Normandy landings. Casarès, a 21-year-old Spanish exile, was starring in Camus's play The Misunderstanding Le Malentendu A Love in Exile: Both were "outsiders" in France; Camus was an Algerian-born
: The letters were kept by Casarès and eventually sold to Camus’s daughter, Catherine Camus , who edited the collection for publication by Gallimard in 2017. Accessing the Text (PDF & Translations) @casarescamuscorrespondence on Tumblr
The letters, published decades later by Camus’s daughter Catherine, reveal a relationship defined by "truth and the absolute".