In a new book, the former US ambassador to the European Union Gordon Sondland defends his conduct around Donald Trump’s first impeachment, derides Democrats for their investigation of Trump’s attempt to extract political dirt from Ukraine – and calls his former boss a narcissist and a “dick”.

Sondland also takes aim at Mike Pompeo, Trump’s secretary of state, who is now a potential candidate for the Republican presidential nomination in 2024.

Sondland criticises Pompeo for firing him over his impeachment testimony and allegedly reneging on a promise to pay his legal fees. Sondland also hits Pompeo for not inviting Volodymyr Zelenskiy, the president of Ukraine, to Washington when the Russian foreign minister visited twice under Trump.

Sondland, a hotelier, donated $1m to Trump after the 2016 election and became EU ambassador two years later. His memoir, The Envoy: Mastering the Art of Diplomacy with Trump and the World – “pause here to allow 10,000 career diplomats to roll their eyes”, the Washington Post quipped in May – will be published on 25 October. The Guardian obtained a copy.

Retelling Trump’s first impeachment, Sondland describes efforts to push Ukraine to investigate Trump’s enemies, including the role of Rudy Giuliani, Trump’s personal attorney.

He rejects criticism from the whistleblower, Alexander Vindman, and ex-Trump advisers John Bolton and Fiona Hill, who in her own impeachment testimony memorably said Bolton, the national security adviser, mentioned Sondland was helping to “cook up” a “drug deal” regarding Ukraine.

In testimony, Sondland described Trump’s attempted quid pro quo: a White House visit for Zelenskiy and the release of military aid in return for investigations of targets including Joe and Hunter Biden.

Sondland now insists there was nothing unusual about this, writing “Quid pro quos happen all the time” and quoting – bizarrely – as evidence both the comedian Jerry Seinfeld and “studies that show when married men pitch in and clean the bathroom, they have more sex”.

But his testimony earned the ire of Trump loyalists including Jared Kushner, the president’s son-in-law, who Sondland suspects may have told Pompeo to fire him.

As for Pompeo, “I knew that the second I had mentioned the secretary’s name in my testimony, he would be pissed that I had dragged him in. But for me to have testified in any other way would have amounted to a series of false statements. Once I made clear Pompeo’s knowledge of what was going on related to Ukraine, I surmise the secretary … wanted me out.”

Discussing his time as ambassador, Sondland says Trump was “essentially right about many things, including how out of whack our relationship with Europe has become”.

But he also attributes Trump’s shortcomings as a leader, including an “inability to clearly explain things”, to factors including his narcissism. On that score, Sondland describes reminding Trump in 2016 that “you were kind of a dick to me when we first met”. Trump, he says, said he hadn’t thought Sondland important enough to be nice to.

Working for Trump, Sondland says, “was like staying at an all-inclusive resort. You’re thrilled when you first arrive, but things start to go downhill fast. Quality issues start to show. The people who work the place can be rude and not so bright. Attrition is a huge problem. And eventually, you begin to wonder why you agreed to the deal in the first place.”

In the vein of tell-alls by bigger Trump players and accounts by Washington reporters, Sondland describes instances of bizarre behavior.

Trump is shown baffling a group of German auto executives by complaining that the seats in their cars have become too hard to use.

“There’s too many damned buttons and knobs,” Trump said. “… What’s wrong with the old-fashioned grab bar, under the seat? Forward. Back. That’s all you need!”

Sondland says the outburst met with “awkward silence”, before Dieter Zetsche, of Daimler, mollified Trump by saying facial recognition technology would soon negate the need for twiddling with buttons, knobs or bars.

More seriously, in describing preparation for meeting the president of Romania in August 2019, Sondland describes how Trump dodged briefings.

“When I get to the Oval Office,” he writes, “the door is open, country music blasting from inside. Trump, sitting at the Resolute Desk, catches a glimpse of me … and beckons, ‘Get in here and tell me which song you like.’

“An aide is … with him, her face like a deer in headlights. ‘He’s choosing which song to use for his walk-on,’ she manages to yell over the noise. He’s vetting the theme music for his next rally. Really. Trump does focus on some details, and this is an important one. Never mind that the Oval Office sounds like a country western bar, and we are supposed to be prepping for a visit with a foreign leader. He skips forward through a couple of tracks.

“‘Mr President, [Klaus] Iohannis is showing up any minute. Don’t you want to be brought up to speed?’ I yell, scanning my briefing paper. At this moment, a group of officials and dignitaries are gathered in the Cabinet Room for an advance discussion, waiting for us. DJ Trump gives me little further response, so I walk down the hall to meet the others.”

Later, Sondland gave Trump “a few quick tidbits about the president of Romania and how we’re friends with them because we’re both opposed to a natural gas pipeline that Vladimir Putin wants to build from Russia to Eastern Europe”.

As the two men waited for Iohannis to arrive, Sondland says, Trump “pull[ed] out a box of Tic Tacs” and “scarf[ed] them down”.

Sondland said: “Aren’t you going to share?”

“Slightly sheepish, Trump pulls out the white mints and shakes some into my hand. When you call him out on not acting like a normal person, it catches him off guard – and then he kind of likes it. People do it too infrequently.”

• This piece was amended on 14 October 2022. It initially said, wrongly, that Mike Pompeo twice invited the Russian foreign minister to Washington.