"Julian Assange: The Unauthorized Autobiography" went on sale in Britain Thursday - against the wishes of Assange, who condemned his publisher for releasing it.
In the book - written by a ghostwriter who conducted 50 hours of interviews with the WikiLeaks chief - Assange says "I may be a chauvinist pig of some sort but I am no rapist."
He says his two accusers "each had sex with me willingly and were happy to hang out with me afterwards."
Assange, 40, claims a Western intelligence contact warned him that the American government, angered by WikiLeaks' release of secret documents, was considering dealing with him "illegally" through rigged drug or sex allegations.
But he also says the sex charges may be the result of "a terrible misunderstanding that was stoked up" between his accusers.
WikiLeaks and its silver-haired frontman shot to worldwide prominence with a series of spectacular leaks of secret U.S. material, including the publication of about 250,000 classified State Department cables.
Assange has also become enmeshed in financial and legal woes, including the allegations of rape and sexual misconduct made last year by two Swedish women.
Assange was arrested and briefly jailed over the allegations in Britain in December. He 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. A ruling is expected within weeks.
The book, for which Assange says he agreed to advances of more than $1 million, was intended to help salvage WikiLeaks' precarious finances.
But after seeing the first draft, Assange got cold feet. Attempts to renegotiate the book deal were unsuccessful.
Assange accused his British publisher, Canongate, of "opportunism and duplicity" for publishing the unfinished book without his approval.
In a statement released to The Associated Press, he said the publisher had acted "in breach of contract, in breach of confidence, in breach of my creative rights and in breach of personal assurances."
Canongate said that since Assange had not repaid his advance - which was handed over to lawyers to help pay his legal fees - it had decided to publish the book.
Assange's U.S. publisher, Alfred A. Knopf, said it had canceled its contract with Assange and would not be releasing the memoir.
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 publishing director Nick Davies defended it as a "nuanced and balanced portrait" of a complex individual.
"He has been portrayed as this Bond villain or a character from a Stieg Larsson novel ... but what comes through here is this very human portrait of Julian, warts and all," he said.