Verified answer

It's not true. He hasn't been dead long enough for this to be in the public domain.

His estate still owns the rights, which means anyone except his publisher is likely to turn this down out of hand. Most likely someone also owns the movie rights, although it's so easy to ripoff the main idea that they would largely be worthless.

I don't see the publisher looking for an amateur sequel to the book, but they might be willing to contact the heirs of the estate with your proposal. Offer them cash up front and a cut of the royalties and they might agree to the idea.

The US copyright for a book published in 1924 expires 95 years later, i.e., at the end of 2019. This presumes it was published in the USA with proper copyright notice and renewal was properly filed 28 years later.

IT HAS NOTHING TO DO WITH WHEN THE AUTHOR DIED. Under USA copyright law, that rule only applies to works published after 1977 or unpublished works.

Add: That being said, the answer to your question is that a "sequel" is not a "copy" but might be a "derivative work", or may include copied fictional "characters" or other creative elements of the original that would infringe copyright unless a license were obtained.

No, the book is not free and clear to use as your springboard.

The Connell estate owns the rights, so a member of his family may be holding onto them, or even the publisher of the book may have the rights. You would need to contact the publisher of the book and ask who the rights belong to to find out, at that point you can contact those people and ASK if you can write a sequel, but even if they say yes, you would owe them a percentage of the income off the book.

You can't write books based off the Narnia books, you can't write books based off Tolkein's Lord of the Rings books, or a sequel to Bram Stoker's Dracula either. For the same reason. The rights are still held by someone.

Whoever told you that didn't know what they were talking about. Copyright lasts for a number of years after the author's death (70 in most countries). If you want to publish a sequel to The Most Dangerous Game, you'll need permission from whoever owns the copyright now - probably Connell's heirs, unless they sold it to someone else. It's extremely unlikely that you'll get this permission unless you're already a well-known author.

Connell died in 1949, so his work is probably still in copyright. I say "probably" because US copyright law was out of step with the rest of the world until the 1980s. Before that, copyright lasted for 28 years from publication. It could be renewed once for another 28 years, but most works weren't, because they earned most of their income in the first few years, meaning renewal wasn't worth the time or expense. So it might've gone out of copyright in 1952 (28 years after it was published in 1924). If so, it wouldn't have gone back into copyright when the US switched to a life + x years system.

The simplest way to figure out whether it's out of copyright in the US is to see whether Project Gutenberg has a copy. But you should probably consult a lawyer before committing a large amount of time to writing a sequel.

EDIT: Actually, Bram Stoker's work is out of copyright, as he died in 1912. Tolkien and C S Lewis are still in copyright, though.

Who is dead? Is Richard Connell dead? Who published his book? Does the publishing company own the copyright?

If any one of these is still "alive" and owns the copyright, then you cannot make use of any of the characters or plot elements.

Years ago, two authors wrote a book called "Everybody Goes to Rick's." The story was set in Lisbon. A movie studio bought the rights from the authors and made it into a movie, "Casablanca." The authors wanted to write a sequel, but the studio sued to stop them. The authors had sold the rights.