James Clapper was eating lunch in Muscat, Oman, on November 9, 2016, when at 2:31 am EST Donald Trump was declared the winner of the presidential election. Clapper was on one of his final trips abroad at the end of a 54-year-long career in the military and intelligence, working with allies to shore up US interests overseas. Although he didn’t know it at the time, the upcoming presidential transition would make the retired Air Force general and director of national intelligence more famous than he ever was when he worked in government.

Today, he has become an outspoken critic of the Trump administration, a regular—and particularly fiery—voice on cable news, questioning the president’s moral and mental fitness for office. In turn, he’s become the embodiment of Trump’s “deep state,” condemned by name regularly on the president’s Twitter feed. It’s a role that Clapper himself finds puzzling, as he recounts in his new memoir Facts and Fears: Hard Truths From a Life in Intelligence. He never intended to write a memoir; indeed, when I spent weeks interviewing Clapper and following him around before the election for what at the time was the sole long-form profile of him ever written, he told me that his only real hopes after leaving office were to fade into private life and clean out his basement.

Yet he says he felt called to write the book after witnessing the first months of the behavior of the man elected during his Oman trip. He has remained a public face during the nearly 18 months since he left office, becoming increasingly outspoken as the president has both publicly attacked his former colleagues in the intelligence community and denied the increasingly damning questions surrounding his campaign’s contact with Russians during an election where Russian intelligence agencies and propaganda outlets, like the Internet Research Agency and the state TV network, RT, spread disinformation and sowed conspiracies aimed at harming Hillary Clinton and helping Trump. As Clapper writes, in explaining his decision to write a memoir, Trump’s embrace of Russia “made me fear for our nation.”

Meanwhile the behavior in office of Trump himself has increasingly disgusted a world-weary Clapper. Retirement from public life ended up coming at a worrisome time for him, he writes. The America he had long sworn to protect turned out to be under unprecedented assault from within. “My journey of 76 years had led me to a place that should be home, and I’d found that the foundation of the home was beginning to crumble and the pillars that supported its roof was shaking,” he writes. “We have elected someone as president of the United States whose first instincts are to twist and distort truth to his advantage, to generate financial benefit to himself and his family, and, in doing so, to demean the values this country has stood for.”

While his book doesn’t shrink from direct criticism of the new president and an administration that prizes “alternative facts” and condemns all dissenting views as “fake news,” the most insightful and important part of Clapper’s book is not the two chapters at the end on Russia and Trump’s election—which no doubt accounts for how his memoir hit No. 1 on Amazon the week of its release—but the sustained argument that Trump is merely a particularly acute and deadly symptom of a longer and, to Clapper, worrisome trend in American society.

American intelligence services have long tracked the rise of what Clapper calls “unpredictable instability,” but now the US appears to be suffering from the same malady. “The United States had begun to show many of the same characteristics of instability we used to assess other nation-states,” he writes, including rising income inequality, an increasingly restive population of young people who couldn’t find work, a rural-urban divide, and declining political discourse.