The sale was timed well with the release of her upcoming novel Go Set a Watchman in July. Lee is known for being incredibly private, with letters such as those she sent to fan Don Salter having been sold at Nate D. Sanders Auction House in 2011 a rarity, as reported by the Los Angeles Times.

Harper Lee Image via Harper Lee
Image via

The letters had an estimate of $250 000. Head of Christie's department of books and manuscripts Tom Lecky said in an interview with the New York Times: "What we have in this archive is a deep and unguarded correspondence. She's not putting on a persona."

In one of the letters Lee wishes to thank a reviewer of To Kill a Mockingbird but admits "one is not supposed to be aware that critics, reviewers, and English teachers exist."

Charles J. Shields, the author's biographer commented: "They're precious, because she published so little. The downside is that it may break the seal on a lot of questions she doesn't want answered. It's going to cheapen her legacy if personal letters keep popping up all the time."

Michael Morrison, publisher and president of HarperCollins, reportedly told the New Yorker prior to the sale "I doubt that she would be very happy to hear that the letters are being sold.''

The six letters Lee's architect friend, Harold Caulfield sent between 1956 and 1961, during the time Lee penned To Kill a Mockingbird.