As a student of Russian in the 1970s, some of my favourite books were well-thumbed volumes of prison stories - books by Solzhenitsyn, Ginzburg, Shalamov - that documented both the brutality and the incongruous humanity that prevailed in the communist labour camps.

"Siberia" and "Gulag" became synonymous with the evils of the Soviet Union.

It is sad to see that two decades since the end of communism, Russia should again be producing prison literature. Penguin have released a volume whose very cover - a sparse, pixelated, black-and-white picture of its author, Mikhail Khodorkovsky - looks like an intentional throwback to the Soviet era.

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Khodorkovsky was modern Russia's most famous political prisoner. Once one of the world's richest people, he disappeared into the Gulag just more than 10 years ago, having enraged Vladimir Putin by using his enormous wealth to challenge him politically. He was not, of course, as per Russian tradition, charged with a political crime, but with embezzlement and fraud. When his first prison term was nearing its end, Putin's puppet courts found him guilty of more crimes, to keep him behind bars - it seemed - indefinitely. "A thief should sit in jail," Putin famously declared.

Then, at the end of last year, as Putin sought to soften his image ahead of the Sochi Olympics, Khodorkovsky was suddenly released - woken by guards in the middle of the night and flown to Berlin. Far from demonstrating new-found respect for the rule of law, however, Putin's gesture seemed to demonstrate his unassailable power: I can take freedom away, and I can give it back.

Remarkably, Khodorkovsky's first book to appear since his release does not mention Putin's name once. It is as if his years in the Gulag have raised him above politics or thoughts of revenge. Rather, he presents a sympathetic gallery of his fellow prisoners - and reminds his readers that one in 10 of the male population in Russia passes through the prison system at some point in their lives. He shared cells and workshops with murderers, fraudsters, gangsters, Nazis, junkies, dealers, thieves and informers, all facing their closed world of hopelessness and violence in their own ways.

Police investigators operate among the prisoners. Khodorkovsky describes one: "He hits people like a true professional, leaving minimum trace, though the recipient spends a week groaning and pissing blood. But no one reckons this 'talking to' is particularly bad. The general opinion is that he's not unusual; 'freelance operatives' are far rougher."

The prisoners endure it silently… until one day they burn the camp down. The stories are essentially morality tales - there are those who sell their souls to the authorities and those, even murderers, who win Khodorkovsky's admiration because they retain their humanity inside prison and refuse the authorities' orders to betray their fellow inmates, even enduring beatings to preserve their integrity.

Since his release, Khodorkovsky has kept a low profile, but as Richard Sakwa's masterly biography shows, he is a man of huge ambition. One wonders just what role he will play eventually in his country, for Putin And The Oligarch portrays a man who reinvents himself constantly. Sakwa traces his development from communist-era speculator to post-communist wheeler-dealer and oil tycoon, to philanthropist and regime-critic, to political prisoner and ultimately to what the author calls "the conscience of the nation".

Most fascinating is the latter half, which charts Khodorkovsky's "personal and political odyssey" during the decade spent in prison, as he lost interest in business and making money, and focused instead - like so many political prisoners before him - on the fate of his country.

Curiously, for a man who made his vast fortune in the period of "robber capitalism" during the 1990s, Khodorkovsky is no supporter of unfettered free markets, but rather a left-of-centre social-democrat, advocating a strong state and high taxes for the super-rich. He no longer sees himself as a businessman at all, but as a member of the intelligentsia, whose role in Russia "is not to struggle for power but to change society".

Sakwa wonders what might have happened if Khodorkovsky had been released earlier, at the time of the mass protests against Putin in late 2011. "He would undoubtedly have acted as a unifying force for the opposition (like Andrei Sakharov), combining patriotic and liberal principles, and would have acted as a symbol of resistance to the regime as a whole."

That was not to happen, and Sakwa speculates that Putin's eventual decision to release him was actually proof of how unthreatened Putin feels, now that the protests have been squashed. Khodorkovsky has not yet returned to Russia, but my guess is he wants to - and still could - play a major role in Russia's affairs. But not until the Putin regime comes to an end.

Angus Roxburgh's book, The Strongman: Vladimir Putin And The Struggle For Russia, is available in an updated paperback version, from IB Tauris, £12.95.