Here's what you might be looking for:
* Chapter 23: This is a significant chapter where Mr. Darcy's first letter to Elizabeth is revealed. It's a pivotal moment in the story as Elizabeth reads Darcy's explanation of his interference in Wickham's courtship of Lydia.
* Chapter 50: This chapter focuses on the second letter from Mr. Darcy, which is a proposal to Elizabeth after she has received news of Lydia's elopement and subsequent marriage.
* Chapter 56: This chapter contains the letter from Mr. Darcy to his aunt, Lady Catherine, revealing his marriage to Elizabeth. This letter is important because it showcases his defiance of Lady Catherine's disapproval and his commitment to his love for Elizabeth.
Beyond these key letters, many other letters are mentioned throughout the novel. These letters play a part in the development of the characters and the advancement of the plot. For example:
* Chapter 1: The novel opens with the news of Mr. Bingley's arrival, conveyed by a letter to Mrs. Bennet.
* Chapter 15: Mr. Collins proposes to Elizabeth via letter.
* Chapter 26: Elizabeth receives a letter from Jane, informing her about Mr. Bingley's departure from Netherfield.
Let me know if you have any other questions about Pride and Prejudice!