His book tells the story of a young man raised in a strict Muslim family in the Israeli-occupied West Bank, in the folds of the Hamas movement.
But he lands in an Israeli prison before he is 20, experiences Israeli torture, but also witnesses torture by Hamas inmates against other Palestinians.
A young Palestinian's rage against Israeli occupation is soon matched by growing hatred of what he sees as the corruption of the Palestinian Authority, the violent ideology of Hamas and finally the precepts of his own Islamic faith.
His mood is still surprisingly upbeat.
"I am more optimistic than at any time in the past, and hopeful about the future. I am sure I will help my people as I helped them in the past, even though they didn't appreciate it."
But he expressed hope that one day they would, even if it was not in his own lifetime.
Appearing relaxed, and dressed casually in jeans and an open-necked shirt, 32-year-old Mosab said he wrote this book because what he did had "opened a thousand questions in everybody's mind".
He makes the bold assertion that in a decade of spying for the Israeli intelligence agency Shin Bet, he served his own agenda, not theirs.
"This is a dangerous statement," he boasts, "but I say it with a lot of confidence."
Sheikh Hassan Yousef disowned his son from his family
He describes his agenda as "stopping bloodshed" - disrupting Palestinian suicide bombings against Israelis, and Israel's assassination of Palestinian leaders, including his own father.
He claims to have stopped then-Israeli Prime Minister Ariel Sharon from killing several key Hamas members, and said he saved the life of current President Shimon Peres. He said he had to do "the right thing".
But this week his father, Sheikh Hassan Yousef, who is in an Israeli prison, disowned his son on behalf of the entire family.
"This is really hard," Mosab admits. "On the eve of releasing a book, I should celebrate with family members."
But he believes his problem is not with his father, who has clearly been the most important person in his life.
"My problem is not with my father, but his God."
'Not in hiding'
For a convert who speaks so strongly against Islam, and what he sees as its support for acts like suicide bombings, he shows no fear aside from the presence of his bodyguards.
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