Few political memoirs qualify as warts-and-all portraits, and The Costello Memoirs is unlikely to be one of them. Indeed, on the strength of the excerpts published yesterday, this book is replete with self-serving justification and convenient oversights. Of WorkChoice, the industrial relations package that more than any other issue sealed the Coalition government's doom, there is barely a mention.

The chief interest in the memoirs lies, inevitably, in its depiction of Costello's politically effective but personally rocky relationship with Howard. In 1995, in the interests of party unity, Costello agreed not to stand for the Liberal leadership, allowing Howard an uncontested accession when the Coalition was virtually assured of winning the next election.

Apparently, Howard gave a verbal undertaking to step aside for Costello sometime in his second term, but it was heard by only two or three people and never formalised. In the event, Howard, citing the vagueness of the promise and other convenient excuses, never returned Costello's favour even when it became apparent in 2007 that the Liberal Party was headed for defeat.

Costello says, correctly, that Howard's continued refusal to step aside, for purely selfish reasons, damaged the party, and also says that had he became leader (even as late as September last year when a delegation of senior Liberals told the prime minister it was time to go) he could have led the Coalition to victory in the 2007 election.

Costello could legitimately have challenged Howard midway through the Government's second term in 2000, but did not because he lacked the numbers in the party room. This thin support had always handicapped Costello's leadership ambitions but, even when it became accepted wisdom within the party that it could not win the 2007 election with Howard as leader, Costello refused to beard his leader.

He now says he held off out of a sense of loyalty to the party. It's a curious rationale, given that by choosing inaction Costello was actually being loyal to Howard. And it could hardly be called an act of loyalty to the Liberal Party for its deputy leader to stand by and allow it to head towards an electoral precipice without taking action to head off the disaster.

That Costello chose not to act then, or even later when the leadership was his for the asking, suggests he never really wanted the job. When he announced he would not seek the leadership the first time round, some commentator ventured that he was the best leader the Liberals never had, but posterity, informed by this book, is likely to reach a different conclusion: that he was a politician who lacked the courage of his convictions, and was ultimately a pushover for more skilled politicians such as Howard.