Love Letters on Blue Paper

Why has Sonia taken to writing letters to her husband, posted to him in the letter-box just outside their house – love letters, on blue paper, recalling with increasing vividness the early days of their courtship and marriage?Why has Sonia taken to writing letters to her husband, posted to him in the letter-box just outside their house – love letters, on blue paper, recalling with increasing vividness the early days of their courtship and marriage?