'Chaos and ineptitude' in Trump White House: Author on 'Powerhouse Politics' Chris Whipple is the author of a book on White House chiefs of staff.

In the wake of all the high-profile turnover, Chris Whipple, the best-selling New York Times author on White House chiefs of staff, describes the Trump administration as “chaos,” and President Donald Trump as “a human wrecking ball.”

“[The first year of this presidency] was a completely broken White House. It couldn’t pass legislation, it couldn’t issue executive orders that were enforceable, it couldn’t get anybody on the same page, it couldn’t prioritize the president’s agenda, nobody knows what the agenda is to this day,” Whipple told ABC News’ Jonathan Karl and Rick Klein on the “Powerhouse Politics” podcast.

Whipple said the result of such “madness” has been “the most dysfunctional, least accomplished White House.”

“I think it’s chaos and ineptitude at levels we’ve never seen in modern history, maybe in history.”

In his book, “The Gatekeepers: How the White House chiefs of staff define every presidency,” Whipple details interviews he's done with 18 chiefs of staff and two former presidents. A newly-added chapter includes interviews with Trump’s former chief of staff Reince Priebus and former chief strategist Steve Bannon.

And he doesn't mince words about Trump's current chief of staff John Kelly, who replaced Priebus.

“Trump needed an empowered chief more than any of his predecessors because he came in with absolutely no idea how to govern. He needed somebody who was empowered. He failed to understand that he needed to empower Reince Priebus. Kelly, of course, is another story,” Whipple said, adding, “In fairness to Priebus, I think he threw his body in front of some bad ideas.”

“In my mind, Kelly is really almost the greater failure because Kelly was empowered in a way that Priebus never was and I think he’s failed the job by almost any measure,” said Whipple.

“You have to be really politically savvy and I don’t think John Kelly has demonstrated any political savvy since he’s taken over the job. I think he’s out of his depth," Whipple said. "His own narrow definition of the job was to make the West Wing more efficient and manage the paper flow. We look up and there are 30 people without security clearances including the guy who’s in charge of Middle East peace. So it’s a disaster,” Whipple said.

"Kelly has failed to help Trump understand that there's a difference between campaigning and governing."

"I think that Kelly has failed even by his own limited definition of the job, which was to make the trains run on time because clearly, the trains are off the tracks now. I think he's failed in a larger sense of telling Donald Trump hard truths and helping him to govern. But I'm not sure if he's going anywhere anytime soon because, you know, as we've seen with Trump, he blows hot and cold--you're in the doghouse one day, you're out of the doghouse the next. I think Kelly is probably okay for the time being. And who in his right mind or her right mind, given the nature of this president, would want to step into those shoes?"

Turning back to the president, Whipple slammed what he said is Trump’s lack of regard for the role a chief of staff plays in helping a president govern, calling Trump “a slow learner.”

“Trump still doesn’t have a clue about governing. He thinks it’s all about campaigning and dividing and demonizing,” said Whipple.

Whipple is a former Peabody and Emmy Award-winning television producer, including for ABC News, according to his website.

The latest edition of his book, with the new chapter on the Trump presidency, is now available.