Rome (CNN) -- Amanda Knox's ex-boyfriend and murder trial co-defendant revealed in a new book that he sometimes questioned her innocence because of her "bizarre behavior" the day a British student was found dead in their apartment.
Raffaele Sollecito's memoir, "Honor Bound: My Journey to Hell and Back with Amanda Knox," is the first book written by anyone directly involved in the Meredith Kercher murder trial in Perugia, Italy.
Kercher, a 21-year-old British student, was found stabbed to death in the Italian apartment she shared with Knox, now 25, of Seattle.
Sollecito and Knox were convicted of Kercher's murder in 2009 but set free on appeal in 2011. They face a final high-court decision in March.
Rudy Guede of Ivory Coast was convicted separately in 2008. His conviction was upheld on appeal in 2009.
Sollecito's book draws heavily on diaries he kept and letters he wrote to friends, family and his hometown newspaper during his years in prison, the preface says.
He chronicles the day of the murder, admitting that he and Knox smoked marijuana that afternoon, which he says he regretted because it clouded his memory of what happened. While maintaining his innocence, he says he does not clearly remember even if Knox spent the night with him.
He and Knox made mistakes the morning of the discovery, including trusting police investigators, he writes.
Sollecito writes that at times, he was uncomfortable with Knox's "bizarre behavior," which he says prosecutors used against both of them.
"Of all the things that Amanda did that day, nothing attracted more criticism than her failure to raise the alarm as soon as she saw so many things out of place," he writes. "It wasn't just the police who attacked her. Many Italians, including most of my family, could not fathom how she could go ahead with her shower after finding blood on the tap, much less put her wet feet on the bath mat, which was also stained, and drag it across the floor."
Neither he nor Knox had solid alibis for the night of Kercher's murder, Sollecito writes.
"We had no real alibi for the night of November 1 except each other, and we did not have lawyers to protect us, and we seemed to have a propensity for saying things without thinking them through," he says.
Sollecito describes his doubt about Knox's innocence at times, referring to the night the two were arrested.
"When I first found out about what Amanda had signed her name to, I was furious," he writes. "Okay, she was under a lot of pressure, as I had been, but how could she just invent stuff out of nowhere?"
He gives an account of his life inside several Italian prisons, where he befriended rapists and murderers, played with cockroaches and scrubbed the cells of dirt and mold.
While sharing his family's personal stories and sagas during the lengthy trial, the book gives very little attention to the evidence presented in court.
The revelations include how he distrusted the lawyers his father hired for him. They were intent on getting Sollecito to abandon Knox and accuse her of the murder, he wrote.
At one time after the first conviction, Sollecito's father sought the help of a private lawyer not connected to the case, who spoke to Perugia prosecutor Giuliano Mignini about striking a plea deal to cut Sollecito's sentence in exchange for evidence against Knox.
Sollecito's lead attorney, Giulia Bongiorno, a prominent parliamentarian, almost walked off the case because of the backroom deal.
Mignini declined to comment about the book or the case until the high court appeal is completed.
Sollecito's book is especially hard on Mignini, whom he accuses of concocting a "conspiracy-laden plotline from Umberto Eco" instead of a normal investigation.
He laments the star treatment Knox received, saying the prosecution focused squarely on his co-defendant. He wrote that he believed he was arrested as a way to get to Knox.
"I don't think the prosecution or police ever seriously thought of me as a murderer," he wrote. "They had one overriding reason to arrest me, throw me into solitary confinement, and threaten me with life imprisonment, and that was to pressure me into rolling over and testifying against Amanda."
Sollecito condemns his treatment by Perugia police who, he says, would not give him food or access to a lawyer during the questioning, even though it was clear to him that they were treating him as a suspect and not just a person informed of the facts of the case.
Sollecito gave several spontaneous declarations during both the original and appellate trials, but he never took the stand in his own defense.
The book offers many details from behind the scenes during the four years between when Kercher was killed and when the two were released, but it does not answer all the questions about what happened that night.
Sollecito wrote that he believed that Guede acted alone in killing Kercher.
In the epilogue, Sollecito recounts how he went to visit Knox in Seattle last fall, but how he was nervous to see her. "I wasn't at all sure it was a good idea and I continued to waver back and forth even after I booked my ticket. We had been through so much; perhaps we owed it to each other to live our lives and leave each other in peace."
Guede is writing a book but does not have a publisher, according to his lawyers. Knox's book is due to be released in the spring.