Titled Ten Years to Save the West, the book is touted as warning against authoritarianism and the threat from “fashionable ideas propagated by the global left”.
In a statement, Ms Truss said: “I want to share the lessons from my experience in government and those international meetings where I was often the only conservative in the room and demonstrate that we have stark choices to make if we wish to avoid a managed decline of the Western architecture that has presided over generations of relative peace and prosperity.”
Her office said she will be writing the book herself, rather than using a ghostwriter.
Out in April, it will be published in the UK by Biteback and in the US by Regnery Publishing as she also seeks an audience in the States.
Ms Truss was forced out of office in October after the budget of £45 billion of unfunded tax cuts outlined by her chancellor Kwasi Kwarteng sparked an economic crisis.
In an interview with the Mail on Sunday, she expanded on her fear for the future of the West, warning of persistent low growth, and that “our culture is being questioned, even basic things like human biology”.
As Donald Trump leads the way as the contender to oppose US President Joe Biden’s bid for re-election, Ms Truss said “we need to get a Republican back in the White House” as she explained she often felt like the “only conservative in the room” in meetings with world leaders.
She added: “You’ve got the global Left which Biden is obviously a key part of, but also the global environmental movement, the Greta Thunbergs of this world, the anti-capitalist movement, and they have been very effective in pushing what is politically acceptable.”
Ms Truss, who became MP for South West Norfolk in 2010, says she still finds it hard to understand what happened during her time in No 10.
“I struggle to compute what happened. Particularly what happened to the Queen. It was extraordinary and it also came off the back of being foreign secretary with the first war on European soil kicking off earlier that year, so 2022 was an extraordinary roller coaster, extraordinary,” she said.
“The whole period from 2010, there have been a lot of ‘pinch me’ moments.”