“The Russian government interfered in the 2016 presidential election in sweeping and systematic fashion,” said the Report on the Investigation into Russian Interference in the 2016 Presidential Election, AKA the Mueller Report. “A Russian entity carried out a social media campaign that favored presidential candidate Donald J Trump and disparaged presidential candidate Hillary Clinton.”

Robert Mueller, the special counsel, did not criminally charge Trump but did not give him a clean bill of health, contrary to misleading claims made by Bill Barr, Trump’s attorney general, in a 24 March 2019 letter – AKA the Barr Report.

Barr’s bad-faith action angered Mueller and members of his team, among them prosecutors Aaron Zebley, James Quarles and Andrew Goldstein. So much so, the three have now written a book of their time at what was once the central maelstrom of American politics.

“The purpose of appointing a special counsel was to shield the investigation from political interference so there would be public confidence in the outcome,” the three men now write in Interference, their look back at their time in the special counsel’s office. “That required the public to see our actual analysis and conclusions, not those of a politically appointed attorney general.”

Under the subtitle The Inside Story of Trump, Russia, and the Mueller Investigation, Zebley, Quarles and Goldstein shed new light on the decisions not to subpoena or indict Trump, who Mueller nonetheless saw as a “subject” – someone “whose conduct is within the scope of the investigation”.

The tenor of Interference is sober, not breathy. Its prose is dry. This is a book by establishmentarian lawyers. Their boss, an ex-US marine and FBI director, earned the sobriquet “Bobby Three-Sticks”, a reference to his name and the three-fingered Boy Scout salute.

Justice department protocols barred federal prosecutors from charging an incumbent president, yet doubts lingered. “The department had twice taken the position, in writing, that a sitting president could not be indicted,” the authors acknowledge. But “if the special counsel’s office had evidence proving Trump truly was a Manchurian candidate, a puppet who was being directed by Russia in a way that was an immediate and ongoing threat, then the public interest in an indictment might be so great as to warrant pushing the department to revisit the [Office of Legal Counsel] opinion in order to safeguard the nation”.

Also, Rod Rosenstein, the Janus-faced deputy attorney general who oversaw Mueller after Jeff Sessions, Trump’s first attorney general, recused himself, reportedly instructed Mueller to limit his investigation to criminal conduct connected with Russia’s election interference.

“This is a criminal investigation,” Rosenstein purportedly told Mueller. “Do your job, and then shut it down.”

Examination of Trump’s prior ties to Russia was outside Mueller’s remit. Furthermore, a 2 August 2017 “scope memo” between Rosenstein and the special counsel gave the deputy attorney general the power to veto new lines of investigation, Zebley, Quarles and Goldstein now disclose.

We know how the story ends. Trump was not charged. Associates were convicted, only to be pardoned. Roger Stone and Paul Manafort remain in Trumpworld. Zebley, Quarles and Goldstein portray Rudy Giuliani, Trump’s personal attorney, as untrustworthy. By the end, Mueller “decided he would never again meet or speak with Giuliani – and he never did”. Giuliani is now under indictment in Arizona and Georgia, for his role in Trump’s attempt to overturn the 2020 election.

Not everyone who worked for Mueller was thrilled with Zebley, Quarles and Goldstein. Andrew Weissmann, a Mueller deputy, now a New York University law professor and MSNBC commentator, has strafed Zebley for being overly cautious, adhering to a narrow reading of the special counsel’s mandate.

In Where Law Ends: Inside the Mueller Investigation, his 2020 memoir, Weissmann hearkened back to the generals who served Abraham Lincoln, comparing Zebley to the “timorous” George McClellan, reluctant to fight the Confederates, while presenting himself as a hero, an approximation of Philip Sheridan and Ulysses S Grant. In turn, Zebley, Quarles and Goldstein see Weissmann as a zealot. Mueller and Zebley knew him but the decision to bring him on board engendered discussion.

“He had a reputation for being unduly harsh with some defendants,” the authors write. In addition, Weissmann was already collecting information on Manafort, “almost as though it had been a hobby”. Maybe “that should have caused us to consider whether he was too interested in the investigation”.

Later, the authors describe Weissmann’s failed efforts to have the Manhattan district attorney resurrect the federal case against Manafort, after he had received a Trump pardon.

As Interference arrives, the US is embroiled in another brutal election. Again, the Kremlin is in the mix. Earlier this month, the justice department indicted two employees of RT, the Russian propaganda machine, as part of “a $10m scheme to create and distribute content to US audiences”. Pro-Trump American lackeys purportedly benefited from such largesse.

Trump continues to brag about his relationship with the Russian leader and his ilk. “I know Putin very well,” he announced at the September debate. “I have a good relationship.”

Also in September, federal prosecutors charged Dimitri and Anastasia Simes in a scheme to evade sanctions and launder money at the behest of Channel One Russia. Dimitri Simes previously led a thinktank with ties to the Kremlin and Trumpworld. His name appeared dozens of times in the Mueller Report, earning a whole subsection, Dimitri Simes and the Center for the National Interest.

As he seeks a second presidency, Trump is unhinged and unrestrained. “I am your retribution,” he tells supporters. “I’m being indicted for you.”

“We were not prepared then,” Mueller writes in his introduction to Interference, “and, despite many efforts of dedicated people across the government, we are not prepared now. This threat deserves the attention of every American. Russia attacked us before and will do so again.”

• Interference: The Inside Story of Trump, Russia, and the Mueller Investigation is published in the US by HarperCollins