The former prime minister's memoir reminds readers how good a raconteur he can be, dishing juicy tidbits every few pages and offering receipts in the form of text and WhatsApp messages.

He's explained away the breaking of confidences by claiming they didn't matter because it was all history - although the old journalist and lawyer insists he was judicious in his choice of which teacups to spill.

His accompanying (now virtual) book tour has tended to look at what might have been if that history was different.

What if Turnbull was still in charge now, dealing with the response to the coronavirus and the economic crisis riding pillion with it?

When asked, he talks about moving sooner to clamp down on the cruise ship industry - something that seems obvious with hindsight and an outsider's perspective.

In any crisis, the public's confidence and trust tend to return to the institutions that form the pillars of our democracy.

Witness the massive jump in Scott Morrison's popularity in polling after the first month when the reality of the virus hit.

Would an election win in 2019 and the popularity boost brought by a crisis have been enough to end the undermining of the "right-wing thugs" within the coalition and the media Turnbull complains about?

It's the biggest, toughest changes to society that benefit most from solid party backing and public support.

Turnbull's solutions to the economic crisis and the way to fund it would have been subtly different from those Morrison is setting up - they are, after all, different men with different backgrounds and views of the world.

Take tax.

Turnbull says in his book he was "always completely open-minded" on an increase to the GST or broadening its base, with the caveat there had to be a demonstrable economic gain.

Then-treasurer Morrison, on the other hand, was bold in his push to lift the consumption tax but, in Turnbull's opinion, "unfortunately nobbled" any chance of that "by front-running policy options in the media".

Questions about the GST, which has remained at 10 per cent in the two decades since its introduction, are again bubbling up after Reserve Bank boss Philip Lowe said Australia had to overhaul the way it taxed consumption, income and land.

Turnbull's pointed advice to those now in power? "Look at options very carefully and do so without frontrunning them in the media, because if you start thought-bubbling these things in the media, they'll get picked off one by one."

Looking back to history, what if Turnbull hadn't been dumped as Liberal leader in 2009? What if Kevin Rudd had been able to pass his emissions reduction scheme - or Julia Gillard's carbon price hadn't run into Tony Abbott's wall of no - and Australia had made strong progress on climate change over the past decade?

Or what if he hadn't been dumped in 2018 and electricity generators were now obliged to create cleaner power?

It wouldn't deal with all of Australia's climate obligations but it would be more than is happening now.

Turnbull drew a parallel this week between the coronavirus pandemic and climate change.

In both instances, politicians are confronted with science but dismiss the severity and delay making the tough decisions needed to act on the reality.

The difference is the biology of coronavirus is so immediate it can't be turned into an issue of belief, unlike the physics of climate change.

"You know, there is nothing so real and confronting as people getting sick right in the here and now before your eyes and dying right here and now before your eyes," Turnbull said.

"There's always been the sense with climate change that it's something for others to worry about.

"Well, it's kind of caught up with us now. We're starting to see the terrible consequences of global warming right now."

Perhaps it's best the past is left to daydreams and the nation gets on with dealing with the reality of the now.

Australian Associated Press