Harper Lee is to publish her second book this summer 55 years after the release of To Kill A Mockingbird.

"Go Set a Watchman" was apparently completed in the 1950s and put aside until it was rediscovered late last year.

It is essentially a sequel to To Kill A Mockingbird, although it was finished earlier.

The 304-page book will be Lee's second and is due to be released on 14 July.

The publisher plans a first printing of 2 million copies.

To Kill A Mockingbird, set around a trial in the racially-divided deep south of the United States, has sold more than 40 million copies.

"It features the character known as Scout as an adult woman and I thought it a pretty decent effort," Lee said in a statement.

"I am humbled and amazed that this will now be published after all these years," she said.

Tom Weldon, CEO of Penguin Random House, said: "To Kill a Mockingbird is one of the most important and enduring books on the Penguin Random House lists and it is no surprise that time and again it is voted best loved by both the reading public and by educators.

"The story of this first book - both parent to To Kill a Mockingbird and rather wonderfully acting as its sequel - is fascinating.

"The publication of Go Set a Watchman will be a major event and millions of fans around the world will have the chance to reacquaint themselves with Scout, her father Atticus and the prejudices and claustrophobia of that small town in Alabama Harper Lee conjures so brilliantly," Mr Weldon added.