Second chance romance about a man who was imprisoned somewhere else and wants to get back with his childhood sweetheart (book title may have had the word "letters" in them)

[Mujidat]

Story about an author who got separated from her childhood sweetheart only for him to come back after years and be forced to work on a romance novel with him
Unknown to her, he was imprisoned in another country all those years, he survived in solitude writing thousands of letters to her which he never sent, he still loves her but doesn't want her to know he was imprisoned, he doesn't want sympathy just true love. This is pretty much what I remember about the book