Jonathan Karp, the publisher of Simon & Schuster, praised the senator in a statement, saying, "This memoir will be about what matters most to him, and I hope it will be regarded as the work of an American hero."
The memoir will be co-written by Mark Salter, a speechwriter and longtime friend of McCain's. The two men have collaborated on several books, including McCain's 1999 bestseller "Faith of My Fathers."
Salter told the AP that the book is not yet completed, but that McCain was "hard at it." He also said the book was originally about "international issues," but that it has evolved since the project began.
"There will still be examples of that in the book, but it will be a little more expansive and reflective about his career and life, the direction of our politics and our leadership in the world, and the causes and values that matter most to him," Salter said.
McCain, who unsuccessfully ran for the Republican nomination in 2000 and was his party's presidential nominee in 2008, has emerged as a frequent critic of President Trump.
In July, he cast a dramatic vote against a Republican attempt to repeal Obamacare with a thumbs-down gesture that drew praise from Democrats and independents opposed to the repeal effort.
On Sunday, McCain, who was imprisoned in a POW camp in Vietnam for 5½ years, took a thinly veiled swipe at Trump in an interview, saying, "One aspect of the conflict, by the way, that I will never ever countenance is that we drafted the lowest income level of America, and the highest income level found a doctor that would say that they had a bone spur."
Trump received a medical deferment from the Vietnam War draft because of a bone spur in his heel.
McCain's book has already undergone a title change. Its original name was "It's Always Darkest Before It's Totally Black," a darkly humorous spin on the optimistic adage "It's always darkest before dawn."