Here, ALAN McCOMBES - the author and Sheridan's former comrade in the Scottish Socialist Party - explains why, as the jailed MSP continues to proclaim his innocence, the extent of Sheridan's lies had to be laid bare once and for all.
It is a book never wanted to write and one that I wish I never had to write.
The story of Downfall is just too raw, too sordid, too dispiriting.
Much of Scotland was fascinated by the dramatic twists and turns of the Tommy Sheridan saga, from its first stirrings in a small office in the back streets of Glasgow to its sensational finale six years later in the High Court of Judiciary.
But for those involved - personally and emotionally - it was a sickening and destructive spectacle. Lifelong friendships were torn asunder. Some people suffered emotional and psychological trauma. Good people were vilified and demonised.
They included the likes of former Sunday Mail columnist, Rosie Kane, one of the warmest and most compassionate people I've ever known.
For years on end, she and her female colleagues were portrayed in the media as a cruel gaggle of stony-hearted witches who had destroyed one of Scotland's favourite sons.
Or people like Keith Baldassara, denounced by Tommy "a scab and a rat" for refusing to lie in court.
Keith had spent years up to his neck in human misery dealing with the MSPs casework on the ground, from dampness and debt to crime and anti-social behaviour
When Tommy received the plaudits and the 'Thank You' cards when the problems were solved, Keith never complained.
His loyalty was as deep as the Clyde, but he was not prepared to stand by while Tommy leapt over the edge, with the rest of his party chained to him.
Worst of all, the most successful left wing socialist party in Europe was reduced almost to smoking ruins.
At its height 150,000 had voted for the SSP. Thousands had sacrificed their time, money and energy to build a movement that, for a time, gave a voice to the people that the mainstream parties had long abandoned – the poor, the sick, the elderly, lone parents, the low paid, unemployed, council tenants.
So Downfall was no pleasure to write but a story that had to be told as a warning and an explanation of that betrayal in all its gory and complex detail.
This book might not have been necessary if Tommy Sheridan had been brave enough, even at the eleventh hour, to put up his hands and take responsibility for his own actions.
Instead, aided and abetted by a noisy little band of supporters, he continues to claim he is the victim of a monstrous frame-up.
That does a grave disservice to those who have suffered from real miscarriages of justice.
And it leaves a chill cloud still lingering over those who have been falsely accused of perjury, forgery and perverting the course of justice as part of a fanatical anti-Tommy plot.
If this book can do anything, I hope it can deconstruct the Sheridan fantasy by offering a blow-by-blow, insider's account of exactly what happened behind the scenes over these sad, sorry years.
This is the truth.The rest is a lie.
Some people have accused me of cashing in. They are wrong. This book wasn't written for money - authors are paid just eight per cent of a book's cover price.
Even if Downfall were to be a best-seller in Scotland, I could have spent the last two years more lucratively pouring pints in a bar.
Nor was I motivated by revenge. If anything, Downfall challenges the idea that Tommy Sheridan alone can be held responsible for the pain and destruction of the past six years.
Many people in politics, the legal system and the celebrity showbiz circuit cheered him along every step on his road to destruction.
In many cases, their complicity was based on ignorance of the facts. But without encouragement Tommy would have been isolated and incapable of inflicting damage on such a scale.
I know many people will be uncomfortable with this book because it challenges their own role in these events but I make no apologies for
I have always believed in redemption. But before there can be reconciliation, there must first come truth.
Downfall will, I hope, set the record staright once and forall.
Perhaps then, we can move on.
Sunday Mail 12 June 2011