The book, currently untitled, will be an intimate chronicle of everything from their careers and courtship to the Jan. 8 tragedy when a gunman shot Giffords in the head during a political event in Tucson, Ariz. Six people were killed in the attack and 12 others besides the congresswoman were wounded. Scribner will publish the book at a date to be determined.
"Since Jan. 8, it's been really touching to us to see how much support there is for Gabby and her recovery, and how much interest there is in how she's doing and her story," Kelly, a Navy captain, told The Associated Press during a recent interview from Texas.
"After thinking about it, and talking about it, we decided it was the right thing to do to put our words and our voices on paper and tell our story from our point of view."
The 47-year-old Kelly most recently was commander of the space shuttle Endeavour's final mission, which ended June 1. His retirement is effective Oct. 1.
"As life takes unexpected turns we frequently come to a crossroads. I am at this point today," Kelly said in a statement posted Tuesday on his Facebook page. "Gabrielle is working hard every day on her mission of recovery. I want to be by her side."
Kelly's announcement is not surprising. NASA is retiring its space shuttle fleet in just another month, and it will be years before the United States has another spacecraft for astronauts to fly.
Giffords, 41, was released from a Houston hospital last week and is set to start outpatient therapy. She had been in the rehab facility since late January, a few weeks after the shooting, and is now living with Kelly at his home in League City, a town 26 miles south of Houston. She will continue outpatient therapy at TIRR Memorial Hermann, the same hospital where she underwent rehabilitation.
Kelly and Giffords are collaborating with author Jeffrey Zaslow, who worked on Randy Pausch's million-selling "The Last Lecture" and Capt. Chesley "Sully" Sullenberger's "Highest Duty." Kelly praised Zaslow as a "good storyteller" and "the best writer" for the kind of book they wanted. Zaslow will interview friends, family members and colleagues of Kelly and Giffords.