Harper Lee's hugely anticipated novel Go Set A Watchman has become Amazon's most pre-ordered title since the final Harry Potter book, The Deathly Hallows.
The novel is due to be published on 14 July – almost 55 years to the day Lee's debut came out to much acclaim. It went on to win the Pulitzer Prize in 1961 before being turned into an iconic film starring Gregory Peck as Atticus Finch.
Go Tell A Watchman is already the number one bestseller on Amazon.com. Though no figures have been revealed, US publisher HarperCollins has ordered an initial print run of two million copies.
However it has some way to go if it is to beat its precursor: To Kill A Mockingbird has sold more than 41 million copies worldwide.
Go Tell A Watchman was actually written before To Kill A Mockingbird, and features many of the characters from her famous debut, not least the tomboy Scout as a grown-up Jean Louise Finch who returns to Maycomb to visit her father.
Lee was advised to set the novel aside and work on a different book from the young Scout's perspective. The manuscript was lost for man years, before being rediscovered last autumn. There has been some controversy around the publication of the book, with claims that Lee is being taken advantage of in her old age. However investigators for the state of Alabama ruled these claims were unfounded.
HarperCollins said the novel follows Jean Louise struggle "with issues both personal and political, involving Atticus, society, and the small Alabama town that shaped her".
Lee, who is 89, has largely avoided the spotlight since the 1960s and is not expected to appear in public to promote the novel.
She has poor hearing and vision and lives in an assisted living facility in her home town of Monroeville, Alabama.