Here are some recommended romance novels for lovers who enjoy reading love letters:
1. "紙短情長,民國大師們的最美情書" by 朱生豪、聞一多、魯迅等: This book is a collection of the most beautiful love letters written by six masters of the Republic of China era.
2. "情書" by 巖井俊二: This book tells the story of two women who start a correspondence through letters, showcasing precious and valuable love.
3. "平如美棠" by 饒平如: "平如美棠:我倆的故事" portrays a pure and timeless love story that remains unchanged by time and circumstances, making it precious and impactful in today's world.
Unfortunately, the provided search results do not contain a comprehensive list of romance novels specifically focused on love letters. However, these three books mentioned above are highly recommended for those seeking romantic stories centered around love letters.