She said there was no set date for its completion.
“The Christchurch Call work on violent extremism and terrorism online is keeping me pretty busy – but I hope when it’s done, it’s the kind of book that would have made a difference to my 14-year-old self.”
Ardern is expected to receive an advance of between $1 million and $1.5 million for the New Zealand and Australian rights.
The only other Kiwi previously in that ballpark has been former All Black Sonny Bill Williams, whose New Zealand, Australian and UK autobiography rights were reportedly sold for A$1m (NZ$1.1m) in 2021.
Publishing experts say most advances in New Zealand are generally between $5000 and $10,000 - perhaps fetching up to $20,000 for the memoir of a well-known politician.
It is understood - if the $1m advance speculation is confirmed - a publisher would likely need to sell more than 100,000 books in Australia and New Zealand to break even.
Former All Black captain Richie McCaw sold more than 120,000 copies, worldwide, of his biography, Open Side, following its release in 2012. At the time, that surpassed the previous long-standing New Zealand bookselling record - for Sir Colin Meads’ 1974 biography, which sold 55,000 copies.