NEW YORK, June 11 — Last year, James Frey and Nils Johnson-Shelton introduced "Endgame” to the Young Adult (YA) genre.

It tells the tale of 12 teenagers who, after a series of catastrophic events, set out on a worldwide search for three ancient keys that will save not only their bloodlines, but also the world.

The YA book went on to become a New York Times best-seller and multimedia phenomenon.

The next instalment in the planned trilogy, "Sky Key: An Endgame Novel”, will hit stores on October 6.

HarperCollins gave a sneak peek of its cover on Tuesday, in conjunction with the release of the paperback version of the first book, along with a brief synopsis of what fans can expect.

In the second book, nine players remain, and they’re on the hunt for two more keys. Their search will take them to New York, Ethiopia and England, as they hunt out the Sky Key.

Frey, who is best known for his partially-fabricated memoir "A Million Little Pieces”, has reportedly sold the film rights for the first book to HarperCollins’ sister company Fox for around US$2 million (RM7.5 million).