Mandelson, whose book was officially launched last night, released seven documents to bloggers dating from 1987 to 1997, including strategy recommendations he made to Tony Blair and Gordon Brown regarding the last ten days of the 1997 election campaign.
That document includes a passage saying that in those last days "spin will be a maximum" premium although in another document, a letter to Blair about his post victory role, he said he did not want to be portrayed as a "spin doctor".
The papers also included a note to Blair on New Labour's historic election victory.
Mandelson has enjoyed a storm of free publicity since his book was serialised in The Times this week. His publisher Harper Collins and The Times are both owned by Rupert Murdoch's News Corp.
The book has been backed by a quirky TV campaign that plays up to Mandelson's "dark prince" caricature. In the ad he is seen sitting in an armchair like the storyteller of some dark and stormy tale.
Mandelson said the ad had "made me famous and also famously ridiculous".
He is understood to have written the book without a contract from publisher Harper Collins but is reported to have received a £500,000 advance.
Rubbing shoulders at last night's launch party were 'The Ghost' author Robert Harris, David Owen, Jon Snow and Andrew Rawnsley. Leading Labour politicians such as Gordon Brown, Tony Blair, or any of the leadership candidates, were not present.
The decision to release papers exclusively to bloggers is an emerging trend and a nod to the growing power of the world of blogs. The Times briefed bloggers ahead of press and before it launched its paywall last month.
For his part, Mandelson, this morning, said the internet had transformed the world of politics and left no hiding places. He added that more often than not it was making politics more transparent and as a result "the varnished truth is no longer an option".
During the briefing he also touched on the power of the TV debates in the 2010 election campaign. The three debates, he said, had transformed the election partly by sucking the oxygen out of the campaign as the debates for the media became the election.
While speaking about Brown, he praised the former prime minister for his world leading role in the fight against the financial crises, which he said would be Brown's legacy, but said he often tripped on the "small things" including communication.
Mandelson spoke about the Mrs Duffy episode, when Gordon Brown called the pensioner bigoted, as one of the few media moments in the election campaign that wasn't about the TV debates.
That moment, he said, and the immediacy of it, crystallised modern politics, where there is no hiding place from the media and reactions are instant.
He compared how fast that story had broken and the speed at which it came to dominate the election news cycle with a story about 1960s prime minister Harold MacMillan who was not faced with such media scrutiny.
When asked by a journalist "what is most likely to blow governments off course?", MacMillan famously replied "events dear boy, events".
A letter from Mandelson to Blair following Labour's 1997 victory