"Go Set a Watchman" and "To Kill a Mockingbird" are both novels by Harper Lee, but they were published at different times and have different purposes. "To Kill a Mockingbird" was published in 1960 and is considered a classic of modern American literature. It is the story of a young girl named Scout Finch who grows up in a small Southern town during the Great Depression, and it deals with themes of racism, prejudice, and social inequality. The novel was well-received by critics and readers and has won many awards, including the Pulitzer Prize.
"Go Set a Watchman" was also written by Harper Lee, but it was not published until 2015, nearly 55 years after "To Kill a Mockingbird." "Go Set a Watchman" is set in the same fictional town as "To Kill a Mockingbird," but it is set 20 years later and focuses on an adult Scout Finch returning home to visit her father, Atticus. The novel deals with themes of racism, prejudice, and social change, but it received mixed reviews from critics and was not as well-received as "To Kill a Mockingbird."
This is not uncommon for publishers to be more interested in publishing a book that they think will be well-received by critics and readers, and "To Kill a Mockingbird" has proven to be a much more successful and enduring novel than "Go Set a Watchman." However, it is ultimately up to the publisher to decide which books they want to publish and which ones they do not.