There are few more important questions for the future of socialism than an understanding of the Soviet Union, its history and achievements and the reasons for its collapse.
It is a cardinal issue of 20th century history, which has a real bearing on 21st century politics.
Far too many historians addressing the Soviet experience are content with superficial or summary judgments which conform to pre-existing political prejudices.
The merit of this book, by two US writers, is that it takes a fresh and penetrating look at the downfall of the USSR — an event that they rightly see as a disaster for the Soviet people and the world alike.
Their main conclusion is that the overthrow of Soviet power was not inevitable and that the problems which undoubtedly existed in the Soviet Union were not systemic but were soluble within the framework of socialism.
The counter-revolution of 1989-91 was primarily the consequence of the mistaken policies followed by the Gorbachev leadership of the CPSU.
A novel and, in some measure, persuasive feature of their analysis is that the social base of Gorbachev lay in what they term the Soviet Union's "second economy" — the growing share of economic activity accounted for by legal and illegal private enterprise, even in pre-perestroika days.
Without a doubt, this sector, which the authors reveal as much larger than hitherto understood, exercised increasing pressure on both the CPSU and the "first" economy — the socialist state sector.
However, the authors make clear that this problem and the other difficulties besetting the USSR in the early 1980s, could have been addressed by other measures than those followed by Gorbachev, which included strengthening the "second economy" through bogus co-operatives and other means.
They commend, as have other socialist commentators, the policies followed by Yuri Andropov during his brief period at the helm of the Soviet state.
There are other aspects of the problem, which, while addressed in Socialism Betrayed, perhaps need to be accorded greater weight.
In particular, the role of imperialist pressure aimed at bringing down socialism requires detailed acknowledgement.
Lenin admitted that the co-existence of the Soviet republic alongside the imperialist powers was inconceivable over any protracted period.
Indeed, the 70 years that the USSR survived in a world — and world economy — dominated by imperialist states which were, taken together, vastly more powerful than the socialist countries was no doubt a far longer period than Lenin might have imagined possible.
Likewise, serious deficiencies in the structure of Soviet socialism as it evolved also played a major part in creating the conditions for Gorbachev's approach becoming ascendant.
These deficiencies were, themselves, broadly rooted in the twin factors of the relative backwardness of Russia and prolonged hostile encirclement and worse on an international scale.
Among the problems this created were a lop-sided economic development which, itself, opened the space for the "second economy" to flourish.
It is wrong, I believe, to attribute such a deep-rooted phenomenon simply to laxness and liberalism on the part of the post-Stalin leaderships of the CPSU.
Similarly, the Soviet Union's isolation and undeveloped social inheritance led to shortcomings in dealing with the national question as well as a failure to address many aspects of women's equality at all.
Socialism Betrayed is sharp although generally well-balanced in its criticisms of the errors and over-optimism of Khruschev, the immobility of Brezhnev and the blundering of Gorbachev. However, a comprehensive accounting of the record of Soviet socialism cannot be coy about the shortcomings of Stalin's leadership as well.
While the authors powerfully dismiss the reformist argument that the Soviet Union fell apart because of a "lack of democracy," the weaknesses in practical working-class control over the leading bodies of political and economic direction, something itself inherited from Stalin's time, certainly made it easier for the powerful forces looking to restore capitalism to achieve their ends.
Naturally, criticisms of Soviet socialism pale into insignificance compared to the post-1991 catastrophe which has befallen the peoples of Russia and the other former republics.
Keeran and Kenny are absolutely right to argue that there should have been, and indeed was, a better way to resolve those problems.
Likewise, any criticisms of the analysis in this well-written book are secondary to acknowledging its great achievement in carrying forward the essential Marxist analysis of the fall of the USSR.
It is the best platform to date for carrying forward discussion of this issue or pre-eminent importance and I would advise every socialist to read it.