The memoir, called "Gabby: A Story of Courage and Hope," is the most personal and detailed look yet at Giffords' struggle over the past 10 months to relearn how to walk and talk, and her painful discovery that 12 others were wounded and six killed during the Jan. 8 attack.
The Associated Press purchased an advanced copy of the book. It is set for release on Nov. 15.
The book is written by Giffords' husband, former astronaut Mark Kelly, but Giffords delivers the last chapter -- a single page of short sentences and phrases entitled "Gabby's Voice" in which she says her goal is to get back to Congress.
"I will get stronger. I will return," she vows. Giffords, 40, stunned colleagues by appearing on the U.S. House floor in Washington on Aug. 1 to vote for the debt ceiling deal, but she has focused most of her time on her recovery at TIRR Memorial Hermann, a rehabilitation center in Houston.
In the book, Kelly recalls trying to tell his wife several times what had happened that June 8 morning, when Giffords was shot in the head while meeting constituents. But she didn't fully understand until March 12.
Kelly asked Giffords if she remembered being shot, and she replied that she did. When he asked what she remembered about it, she said three words: "Shot. Shocked. Scary."
Later that same day, Kelly was reading to her from a New York Times article about her recovery and skipped over a paragraph that said six others were killed. Giffords, following along, knew he left something out and pushed him to tell her what it was.
Kelly writes that after she learned of the deaths, Giffords was overcome with emotion and had trouble getting through her therapy. That night as they lay in bed, she told Kelly that she felt awful about all the people who were killed. He held her as she cried.
Six months later, after being released from the Houston hospital to Kelly's home 25 miles away, Giffords wanted to know who had been killed that day. He warned her that it would be tough on her because she knew two of the victims.
He started by telling her that her staff member Gabe Zimmerman died, which caused her to moan and cry in a wave of emotion. Then he told her about her friend, federal Judge John Roll, and the four other people she didn't know. Finally, he told her that Christina Taylor-Green, a 9-year-old girl born on Sept. 11, 2001, was among the dead.
After she got the news, Kelly writes that he held her as she processed the information and wept.
Kelly recounted the agonizing moments when several media outlets inaccurately reported that Giffords was dead, then described experiencing hope when he learned she was alive and being treated at a Tucson hospital.
When Kelly first saw Giffords after the shooting, he wrote that he was shocked at her state: She was in a coma with her head partially shaved and bandaged, her face black and blue, her body connected to a bunch of tubes. He told her how much he loved her and that she was going to survive.
He also describes the early days in Giffords' recovery and rehab in Texas, saying that the darkest moment came when Giffords panicked because she realized she couldn't talk. Her eyes were wide with fear and she was crying uncontrollably as Kelly tried his best to comfort her and assure her that she would get better.
The book describes lighter moments, like when President George H.W. Bush and his wife, Barbara, visited Giffords at the Texas hospital. Giffords kept replying to Bush with the only word she was able to say: "chicken." At another point, a specialist showed her various politicians to see if she recognized people. When she saw former California Gov. Arnold Schwarzenegger, she said: "Messin' around. Babies."
As she progressed, Kelly said Giffords learned to talk again, reciting the U.S. Constitution and Martin Luther King Jr.'s "I Have a Dream" speech.
The book reveals that because of her injuries, Giffords has lost 50 percent of her vision in both eyes.
Kelly also reveals that the couple was quietly trying to have a baby. Giffords had undergone several rounds of fertility treatments in the last few years and was hoping to be pregnant early in 2011.