The first memoir by a current inmate detailing life inside Guantanamo is to be released next week following a six-year legal fight to declassify the manuscript, extracts of which appeared in The Guardian on Saturday.
In "Guantanamo Diary" Mohamedou Ould Slahi claims he only confessed to involvement in various terror plots, including one to bomb the CN Tower in Toronto, after being tortured and humiliated.
Asked by interrogators if he was telling the truth, he replied: "I don't care as long as you are pleased. So if you want to buy, I am selling," according to extracts of the book, which is to be published in 20 countries, published in the British newspaper.
The 44-year-old swore allegiance to al-Qaeda after travelling to Afghanistan in the 1990s and fought against the Soviet Union-backed regime, but claims he left the group in 1992.
He was detained following the 9/11 attacks on suspicion of involvement in an unsuccessful plot to bomb Los Angeles in 1999.
He was taken to Guantanamo in 2002 following interrogation in Mauritania,Jordan and Afghanistan.
Describing the toll of life inside the jail at the US base in Cuba, Slahi said: "I started to hallucinate and hear voices as clear as crystal. I heard my family in a casual familial conversation?. I heard Qur?an readings in a heavenly voice.
"I heard music from my country. Later on the guards used these hallucinations and started talking with funny voices through the plumbing, encouraging me to hurt the guard and plot an escape.
"I was on the edge of losing my mind."
The detainee's lawyer, Nancy Hollander, explained that her client had never been charged with any crime.
"It's not that they haven't found the evidence against him -? there isn't evidence against him," she said.
"He's in what I would consider a horrible legal limbo, and it's just tragic: he needs to go home."
The American Civil Liberties Union has launched an online petition demanding his release.
"Mohamedou Slahi is an innocent man whom the United States brutally tortured and has held unlawfully for over a decade," said Hina Shamsi, director of the ACLU's national security project.
"He doesn?t present a threat to the US and has never taken part in any hostilities against it," he added.