Distilling a set of arguments he’s been making for almost 15 years, Danner contends that many of the post-9/11 counterterror programs enacted under Obama and George W. Bush have created new, equally troubling problems, “degrad(ing) the country’s values together with its security.”

Though not new, this remains a grave charge, one with the power to incite those on both ends of the ideological spectrum. And given the author’s credentials, it’s worthy of serious consideration. Danner, a UC Berkeley professor, covered the war in Iraq, and his rigorous essays for the New York Review of Books have established him as one of America’s sharpest national security writers.

“Spiral” is a provocative, and often very effective, book. Sifting through the moral, ethical and legal questions raised by Obama’s aggressive use of drones and his failure to close the Guantanamo Bay prison, Danner asserts that the president has not only neglected some of his campaign promises — he’s actually inherited Bush’s knack for unintentionally supplying terrorist groups with recruitment propaganda.

That said, it’s somewhat disappointing that Danner’s assessment of the Obama presidency takes up only a little more than half the text. The rest is given over to a rather stale review of Bush’s counterterror efforts. On one level, this is understandable, especially when you remember that the presumptive Republican nominee for president has vowed to revive the Bush-era “advanced interrogation” methods used in terrorism investigations — tactics that a Senate report called “torture.”

But even as Danner presses a compelling case against the 43rd president, there’s a sense that he’s simply rehashing arguments he formulated years ago — preaching to a choir that has long since convicted Bush in the court of public opinion.

In Danner’s telling, Bush inaugurated a post-9/11 “state of exception,” a period of ceaseless war “during which, in the name of security, some of our accustomed rights and freedoms (were) circumscribed or set aside.” Obama, he says, has accepted the baton from Bush, “normalizing the exception” in the form of “warrantless surveillance of American citizens” and a shortsighted drone campaign in Afghanistan, Pakistan, Yemen and other countries.

Though he “never could have come to office were it not for the unpopularity of the wartime president who came before him,” Danner writes, Obama “has settled into a quietly lethal mode of combat that relies on methods that would have been inconceivable a decade and a half ago.”

The exact casualty numbers from U.S. drone strikes are unknown, but based on reporting from nongovernmental organizations and other sources, Danner says the total might be as high as 5,000. Even “the most conservative estimates suggest that at least one in ten of these have been noncombatants,” he notes.

To Danner, the results of such a program are obvious. Drone killings, he says, “are a stopgap measure, at best disrupting attacks at the cost of nourishing and expanding” terrorist groups’ influence. “It is not in dispute,” he adds, “that these killings of thousands of Muslims, conducted by remote control by a distant superpower, have caused enormous resentment and hatred of the United States in Pakistan and throughout the Islamic world.”

Both Bush and Obama deserve some blame for the rise and spread of the Islamic State, Danner says. The Islamic State “was born of the Iraq War, a war of choice launched by President Bush,” he writes, and “President Obama’s decision a decade later to bomb the Islamic State in order to ‘degrade and ultimately destroy’ it has dramatically helped its recruiting, hastening a vast flow of foreign fighters into its ranks.”

Some of Danner’s contentions are debatable. For instance, if bombing the Islamic State is a bad idea, what’s a better one? But he does propose a number of solutions to the problems he identifies in “Spiral.” For a start, he says the U.S. needs to accept that the Middle East is riven “by its own chaotic internal struggles,” and that it’s probably not “in America’s vital interest to attempt to dominate and guide these” struggles.

To this end, Danner suggests that a pair of broadly worded Authorizations for Use of Military Force passed by Congress after 9/11 ought to be replaced “with more restrictive provisions that would allow for the use of force against specific enemies in specific countries for a stated length of time.” He also calls for an end to the “unceasing drone and special operations campaigns” employed by the Obama administration and a Truth Commission that would investigate the Bush-era torture of terrorism suspects.

These are forward-looking ideas, and they’re among the reasons why at its best, “Spiral” is a timely, valuable book. His evaluation of George W. Bush may feel dated, but when he focuses on our outgoing commander-in-chief’s body of work, Danner provides a vital service in this election season, reminding us that the job of president of the United States grows more complex with each passing year.

Kevin Canfield has written for Bookforum, Film Comment and other publications. Email: books@sfchronicle.com