British publisher Canongate said Wednesday that the book, billed as an "unauthorized autobiography," will be for sale in stores and online Thursday.
Last year Canongate paid Assange, 40, a large sum for the rights to the memoir and Assange began working with a ghostwriter on the book, which he said he hoped would be "one of the unifying documents of our generation."
But the publisher said that as he recorded 50 hours of interviews about his life, Assange became increasingly troubled by the prospect, eventually declaring that "all memoir is prostitution."
Canongate says Assange tried to cancel his contract, but since he has not repaid his advance it is publishing the first draft that the WikiLeaks founder delivered to the publisher in March.
WikiLeaks did not immediately respond to requests for comment.
In December, Assange said he didn't want to write a book, but had been forced into the deal to pay his legal bills and keep WikiLeaks afloat.
WikiLeaks and its silver-haired frontman shot to worldwide prominence with a series of spectacular leaks of secret U.S. material, including the ongoing publication of some 250,000 classified State Department cables.
The publisher said the book traces Assange's life from his Australian childhood through his time as a teenage computer hacker to the founding of the secret-spilling website.
Canongate said the book is, "like its author, passionate, provocative and opinionated."
The Independent newspaper, which will run extracts from the book starting Thursday, said the memoir also deals with events in Sweden in 2010 that led to allegations of rape and sexual molestation against Assange by two women.
Assange is currently out on bail and living at a supporter's mansion in eastern England as he awaits a judge's decision on whether he will be extradited to Sweden to face those allegations.
