Sen. John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE’s upcoming memoir will include the senator’s “no-holds-barred” opinions about the 2016 election and the current state of politics.

“The Restless Wave: Good Times, Just Causes, Great Fights, and Other Appreciations,” was signed by Simon & Schuster in February and is scheduled to be released in April, according to The Associated Press.

“Candid, pragmatic, and always fascinating, John McCain holds nothing back in his latest memoir,” according to Simon & Schuster.

The book will cover McCain’s life and politics since the senator’s 2008 presidential loss to Barack Obama Barack Hussein ObamaDemocratic Senate campaign arm outraises GOP by M in August A federal court may have declared immigration arrests unconstitutional Blunt says vote on Trump court nominee different than 2016 because White House, Senate in 'political agreement' MORE.

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McCain has been a vocal critic of President Trump, a theme that will likely appear in the memoir.

The feud between the two Republicans, which has been ongoing since the 2016 campaign, devolved into Twitter threats earlier this week after McCain delivered a passionate speech slamming “half-baked, spurious nationalism," which many saw as a veiled attack on Trump.

McCain was diagnosed with brain cancer in July and notably returned from treatment to be the deciding vote to kill the "skinny" ObamaCare repeal bill.

The book's tone is a change from the originally planned focus on international affairs and McCain’s work overseas. The memoir was originally titled “It’s Always Darkest Before It’s Totally Black.”

“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,” McCain’s collaborator, Mark Salter, told the AP in an email.

“The original title was an old joke he employed often over the years. But the Senator thought it was too flip for some of the subjects he now wants to address,” he said.