Dirty Politics author Nicky Hager will release his next book on Tuesday, Newshub has confirmed.

The title and topic are still a mystery, but Unity Books in Wellington has confirmed to Newshub it will be revealed on Tuesday at 5:15pm.

"The book is not a sequel to Dirty Politics nor related to the election," Hager said in an email.

"It is a completely different book but nonetheless gripping and important."