NEW YORK • He turned up at the houses of important people unannounced - late at night - to ask for interviews.

Now, the folk in Washington - where secrets can be almost impossible to keep - know what Bob Woodward (above) was up to.

Over the past 19 months, America's most famous investigative journalist had been quietly chipping away at a book that delves into the dysfunctions of United States President Donald Trump's White House.

On Monday, that veil of secrecy was lifted when Simon & Schuster said it would publish Fear: Trump In The White House on Sept 11.

In the book, Woodward's 19th, the 75-year-old journalist and author "reveals in unprecedented detail the harrowing life inside President Trump's White House and precisely how he makes decisions on major foreign and domestic policies", the publisher said.

The hush-hush project derives its title from an off-hand remark that then candidate Trump made in an interview with Woodward and Washington Post political reporter Robert Costa in April 2016.

Mr Costa asked Mr Trump whether he agreed with a statement by then president Barack Obama, who had said in an Atlantic magazine interview that "real power means you can get what you want without having to exert violence".

At first, Mr Trump seemed to agree, saying: "Well, I think there's a certain truth to that... Real power is through respect."

But he added a personal twist: "Real power is, I don't even want to use the word: 'Fear.'"

Woodward, an associate editor at The Washington Post, is deeply embedded in the cultural fabric of American journalism.

He is famed for his Pulitzer-winning reporting at The Post with Carl Bernstein on the deceptions and misdeeds of president Richard Nixon in the 1970s that eventually led to the resignation of the 37th president of the United States.

Their work was immortalised in the film All The President's Men (1976), in which Robert Redford played Woodward and Dustin Hoffman portrayed Bernstein.

Woodward is one of the best-selling American non-fiction authors of the modern era. His most recent work, The Last Of The President's Men, chronicled the story of Mr Alexander Butterfield, a Nixon aide who revealed the existence of an Oval Office taping system.

But with his new book, he will be returning to the sort of endeavour for which he has been best known during his long career: real-time reporting on American power and the presidency.

His previous works on American presidents, including books about Mr George W. Bush and Mr Obama, focused on single, all-important decisions, such as whether to engage in foreign wars.

Fear is expected to be a broader examination of the presidency. It will add to the avalanche of books on the Trump presidency or issues related to his time in office.

Among those that have generated headlines are former FBI director James Comey's book A Higher Loyalty, Michael Wolff's Fire And Fury: Inside The Trump White House, and a just-released book by Mr Trump's former press secretary Sean Spicer called The Briefing: Politics, The Press And The President.

While working on the book, Woodward had kept a lower profile than usual, limiting cable news appearances and staying out of the public eye.

He told friends he had gone back to some of the signature moves of his youthful reporting days.

The work felt like a "rebirth" in the latest chapter of his career.

WASHINGTON POST