After writing To Kill a Mockingbird, Harper Lee mostly kept out of the public eye. She did not release another book for decades and made very few appearances.
She died in 2016. Journalists and literary historians have been attempting to piece together details of the author's life, but they have met with little success. She was a private person and those who knew her have not been willing to talk very much about her or her life.
Lee’s Will has been unsealed but it does not reveal very many details, as Al.com reports in "Harper Lee's will is unsealed but questions about the legend of American literature remain."
Lee's Will directs that all of her assets, including literary property, be put into a previously created trust. Details about the trust are not publicly known. There does not appear to be a way to make them public so we can all see (and learn) what she was thinking about all these years. The trust's beneficiaries and trustee were also not disclosed.
What Lee created is known as a “pour-over Will.” It is a simple way to have assets transferred to a trust after someone passes away. Since trusts do not have to go through probate they can remain very private. Using a Trust can be a great method to use for people who do not want the details of their estates known to the public, as Lee apparently did not.
So the mystery continues and the way her estate was set up it is unlikely we will know much about her estate. Perhaps one day one of her heirs will come forward and share with us all how she shared her wealth and assets among her loved ones. Until then, the mystery remains and we’ll all get to speculate on what really happened to this very private woman.