A letter from Harper Lee to an old friend in which the To Kill a Mockingbird author rages about the “bad taste” and hypocrisy of people in her home town she felt were “trying to turn [her] into a tourist attraction like Graceland or Elvis” has sold at auction for almost £20,000.

The letter is part of an archive of drawings and letters from Lee to Charles Weldon Carruth. Written in 1993 from Monroeville, Alabama, it sees her complain that “what was once a tiny town of considerable character is now six times its size and populated by appalling people”.

She goes on to rail against how locals are raising money to restore the town’s old courthouse, which was used as the model for the courthouse in the film of her novel, and turn it into a tourist attraction. She writes of how she loathes the billboards that have been erected around the town, showing the courthouse and an image of a mockingbird, and says she “nearly had a fit” when she saw one situated at an exit to the interstate highway, calling it “in indescribable taste” and “a fraud on the public”.

“People will drive miles out of their way to look at Monroe County’s heritage, which consists largely of ratty quilts and Mr Pone McNeil’s walking stick made out of a cypress tree,” she wrote. “The hypocrites in charge, not a one of whom I know, say they are doing this to ‘honour’ me. What they are doing is trying to drown me in their own bad taste, and are embarrassing me beyond endurance.”

Lee’s anger at the way Mockingbird’s success was exploited by her Monroeville rumbled on for years. In 2013, she brought a lawsuit against the town’s museum, which attracts 30,000 visitors a year, accusing it of exploiting her fame without compensating her.

Auction house Bonhams said the missive was “a searing letter on the monetisation of Mockingbird in Monroeville … both loving and full of a harsh honesty normally reserved for very close friends”. It is signed by Lee in the persona of Queen Victoria: “Your unamused but loving, Victoria R & I.”

The collection of documents, which Bonhams sold for £19,158, also includes a series of caricatures of Carruth, showing him as various Shakespearean characters including King Lear, Othello and Julius Caesar. They date from Lee’s time at the University of Alabama, where she edited the campus humour magazine Rammer Jammer, and show the obvious affection the writer felt for Carruth. In a 1991 letter, she tells him “you are one of the most special people to me, and you have meant so much to my life”.