Kristin Hannah doesn't write a novel in one clean pass. She builds it in stages, opening with months of research and a detailed synopsis, then drafting and redrafting until the story matches what she pictured. By her own count, that's about ten drafts a book.

The Direct Answer
She researches for months, writes to a long synopsis, then rebuilds the book across roughly ten drafts.
She's broken the timeline down on her official site FAQ: about three months of planning, five months of first draft, then four to six months of revision.

Research First, Then a Synopsis

Before Hannah writes a word of the actual novel, she spends roughly three months coming up with the idea, researching it, and building a loose plan for the spine of the story and the character arcs. For her historical novels, that research runs deep. Books like The Nightingale and The Four Winds demanded real digging into their periods, and she's described chasing historical rabbit holes and taking copious notes, then letting it all sink into her subconscious while theme guides the shape. The planning stage is comfortable for her, a place to explore before the pressure of the page sets in. She only moves on once the story has a clear frame.

The signal to start is a document, not a feeling. When she's written a long synopsis with a clear beginning, middle, and end, she knows the planning is over and it's time to write.

When I have written a lengthy synopsis that has a very clear beginning, middle, and ending, then I know it's time to take the plunge.

Kristin Hannah, The Novelry interview

The Draft, Then Ten More

The first draft, on a good run, takes about five months, and Hannah is honest that it usually includes several wrong starts and do-overs. Then comes the part she likes best, a long stretch of heavy revision she's described as hack-and-burn editing, where she throws out what isn't working and tries something else. Turning that rough draft into the novel she pictured takes another four to six months, and by the end she's typically done about ten drafts. The number sounds punishing. For Hannah it's the cost of getting a book right.

Her revisions can go all the way to the foundation. The Great Alone started as a modern-day story with an unreliable male narrator investigating a crime, and it became a 1970s coming-of-age story about a girl growing up in Alaska. The Alaska setting survived the overhaul. Almost everything else changed. Character is where a lot of that evolution happens, and she leans on dialogue to find it, saying she learns who her characters are by what they have to say.

For how this process fits into her wider habits and hours, see the full Kristin Hannah writing routine.

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