To prepare himself, Mills says he re-read every one of Flynn's books in chronological order and took 150 pages of notes on everything from his writing style to his word choice. For The Survivor, Mills says he plans to continue with the story threads left hanging from Flynn's last book, The Last Man, published in 2012.

"I feel pretty confident that I can produce something that people will love, because my goal is to produce something I would have loved (to read) if I hadn't been asked to write and somebody else had done it," Mills says.

Throughout the series, Rapp survives brushes with death and battles terrorists, who plot to detonate a nuclear warhead in Washington, in Memorial Day (2004) or who seize the White House and take hostages in Transfer of Power (1999). Plans remain in the works to make a Mitch Rapp movie based on 2010's American Assassin, CBS Films spokesman Grey Munford says.

Mills grew up in Oregon, the son of an FBI man, and now lives in Jackson Hole, Wyoming. He says he worries constantly about whether Flynn's fans will accept him.

"As a Vince Flynn fan, you come to know and love that character. As an author, you need to create that," Mills says. "I'd hate to pick up a Mitch Rapp (book) and not have it feel authentic."

In a statement, Flynn's widow, Lysa Flynn, thanked Flynn's fans for their "love, support and patience".

"Vince was very proud of his team and we are confident that Kyle Mills will be a great addition. God bless and keep the faith!" she says.

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