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In just about a month, Harper Lee will publish her highly anticipated second novel, Go Set a Watchman. But before its release, Christie’s will auction off six “exceptionally rare” letters written by the author to her friend Harold Caufield. Four of notes are dated from before she released To Kill A Mockingbird.

According to a release from the auction house, the letters are typed and signed with Harper’s comic pseudonyms like “The Prisoner of Zenda,” “Francesca Da Rimini” and “R. Bouverie Pusey.” One is signed in holograph, “Manning.”

The collection shows major insight into Lee’s life during this time, and in one letter, dated Dec. 12, 1960, Lee reacts to the mainstream success she experienced after To Kill A Mockingbird debuted. “We were surprised, stunned and dazed by the Princeton Review,” she wrote. “All that lovely, lovely money is going straight to the Bureau of Internal Revenue tomorrow…”

Another, dated Nov. 21, 1961, reveals that Esquire turned down her work about “some white people who were segregationists & at the same time loathed and hated the K.K.K.” She wrote in the same letter that she may visit Kansas that January to join writer Truman Capote as he worked on In Cold Blood.

Many of the early letters were written from her home in Monroeville, Alabama, where she took care of her ailing father. She wrote, “Daddy is sitting beside me at the kitchen table … I found myself staring at his handsome old face, and a sudden wave of panic flashed through me, which I think was an echo of the fear and desolation that filled me when he was nearly dead. It has been years since I have lived with him on a day-to-day basis.” It’s widely believed that Lee based the character Atticus Finch off of him.

Four years earlier, she had written about the “ecclesiastical gloom of Monroeville” and missing New York. “Genius overcomes all obstacles, etc., and this is no excuse, but I think the record will show the extent of my output at 1539 York [Ave.]…” she wrote from Alabama. “Sitting & listening to people you went to school with is excruciating for an hour—to hear the same conversation day in & day out is better than the Chinese Torture method. It’s enough to make you give up.”

Christie’s notes that these letters, estimated to go for $150,000-$250,000 on June 12, are the earliest correspondence we’ve seen from Lee. “No other material of this early date–and certainly not with such revealing and personal content–has come to auction in the last 40 years,” the statement said.

Go Set A Watchman was actually written before To Kill A Mockingbird, takes place after the iconic book and focuses on Scout as an adult. When the Watchman was announced, Lee said that her editor at the time encouraged her to write from a younger version of Scout’s perspective, a feat which turned into To Kill A Mockingbird. According to the official book announcement, Watchman follows Scout two decades after To Kill A Mockingbird ends, as she’s “forced to grapple with issues both personal and political as she tries to understand her father’s attitude towards society, and her own feelings about the place where she was born and spent her childhood.” It hits shelves on July 14.