It has been used for everything from a business management manual to toilet paper. But while Mein Kampf has served many purposes, as a pick-up device it is a definite flop.

“I’ve tried the line ‘Do you want to read Mein Kampf with me?’, but I can tell you it doesn’t work,” said Alon Kraus, the son of Holocaust survivors and one of six protagonists in a bold stage version of Adolf Hitler’s Nazi manifesto playing to packed houses across the German-speaking world. A re-enactment of the 44-year-old Israeli lawyer’s real-life attempts to seduce a German tourist on the Sinai peninsula by reading extracts from Hitler’s rambling racist discourse raises the loudest – albeit hesitant – laughs.

Adolf Hitler: Mein Kampf, Volumes 1 & 2, is a bizarre investigation into the life and times of what has been called the most dangerous book in the world.

While it has never been forbidden in Germany to own original copies, distributing it is illegal. However, 70 years after Hitler’s demise, the book’s status will change dramatically at the end of the year when its German copyright expires.

Facebook Twitter Pinterest A scene from Adolf Hitler: Mein Kampf, Volumes 1 & 2 Photograph: Candy Welz

To mark its – nervously awaited – first reissue in Germany since 1945, two Berlin theatre directors decided to look into why Mein Kampf continues to fascinate. “We set out to explore who has read it, how have they read it, and what will happen to it when a new version appears in January,” Helgard Haug, a director with the Berlin-based theatre collective Rimini Protokoll, said before a recent performance at Munich’s Kammerspiele theatre.

Applying its much-praised “documentary theatre” technique – where topics are developed through intense journalistic-style investigation – the group started off “by asking which of us had read it and who had a copy lurking at the back of a bookshelf or in their attic”, Haug said. “Our aim was to take the most open approach to it as possible, to find out above all why it is still considered to be such a mythical book.”

Interviews with lawyers and historians, antiquarian booksellers and the actors’ own families, accompanied by archaeological-style digs everywhere from back gardens to attics, form the backbone of the play. What is revealed is the ubiquity of a work widely considered to have been long since consigned to the dustbin.

Rimini’s explorations took the play’s “real-life experts” – Kraus, a book restorer, a Turkish rapper and a visually impaired musician, among others – to destinations as far afield as the International Antarctic Centre’s library and a bookstall in Bangalore. They found Mein Kampf everywhere, from the “poison cabinet” of Bavaria’s state library, where every request to see one of its 70 copies is scrutinised, to a flea market in Istanbul.

What emerges is a sense of its enduring allure – in some Arabic-speaking countries; in Japan and Turkey, which have manga versions; and in India, where business students are advised to read it as an introduction to modern management. There is also a Hebrew version available for academic study in Israel.

The editions Rimini Protokoll collected are on book shelves of the play’s set. At one point on stage, Christian Spremberg, the blind musician, runs his fingers over a huge braille version from the 1930s and recites some of antisemitic passages, first in a gentle tone then in an insistent bark.

Facebook Twitter Pinterest One of two rare copies of Mein Kampf signed by the young Adolf Hitler, which went up for auction in 2014 in California. It sold for $64,850. Photograph: Frederic J Brown/AFP/Getty Images

From this production, “you learn almost everything that you need to know about Mein Kampf”, said Jens Bisky, a cultural commentator “as well as how to sensibly deal with toxic waste, debunk myths and turn fetishes into banal everyday objects”.

As the protagonists toss editions to each other across the stage – a gold-rimmed one for newlyweds, another on thin paper for soldiers – the audience learn more than 12m copies were sold from Mein Kampf’s first release in 1925 until 1945.

The initial 10,000 copies cost an extortionate 12 reichsmark, “the equivalent of 32 kilogrammes of bread”, said one protagonist, or €300-€400 (£215-£290) in today’s money.

Precisely how many Germans read it is not known but, say experts consulted for the play, the claim by many that they had never even opened it and therefore knew nothing of Hitler’s murderous plans, is bogus. So too is the story that all married couples received a copy: many local authorities could not afford it. However, surveys from 1945 suggest about a fifth of Germans read it from start to finish. At the end of the war, many burned their copies and there is anecdotal evidence that, at a time of widespread shortages, it was often used as toilet paper.

The collective even went to Landsberg, the Bavarian jail where Hitler was imprisoned for treason following the Munich beer hall putsch, and where he wrote his ominous tome. “We found nothing of cell number seven where Hitler did his time,” book restorer Matthias Hageböck recalled. The cell was destroyed, lest it became a place of pilgrimage for neo-Nazis.

The state of Bavaria, which owns the copyright because Hitler’s registered abode was in Munich, spent years blocking efforts to publish new editions of the book, insisting it would inject new impetus into the far-right movement. But German historians have long supported an academically annotated version, insisting it would help rob the book of its allure and help counteract the impact of 20 freely available internet versions.

Finally, after years of procrastination a state-supported version is due to be published by Munich’s Institute of Contemporary History on 7 January. However, the institute is at pains to point out it has made it as “commercially unappealing” as possible.

If its racist content and turgid style are not enough to put people off, the price of €59 means the new version is unlikely to embarrass Germans by becoming a bestseller. And at 2,000 pages long – including 3,700 footnotes – the hope is that only academics and libraries will buy it.

Facebook Twitter Pinterest Adolf Hitler: Mein Kampf, Volume 1 & 2 Photograph: Candy Welz

“It’s about time,” said Sven Felix Kellerhoff, author of Mein Kampf: The Story of a German Book. “By putting it off, they’ve only helped contribute to the myth that it is too incendiary a text for the public to deal with. But we are grown up enough now and we have a responsibility not to brush it under the carpet.”

Others remain nervous. While the book is not believed to be widely read in far-right circles, it is nevertheless said to be a trophy on many neo-Nazi bookshelves. “It’s hard to imagine some shaven-headed neo-Nazi … sitting in front of his computer ... reading the juiciest bits to a blush of boys armed with belt buckles,” Willi Winkler of the Süddeutsche Zeitung has written, “but every ideological fanatic has access to it and from January, it will be possible to hold such nostalgic seances once again over the printed book …”

As to Hitler, it is well-documented that Mein Kampf made him a fortune – more than 12m reichsmark – not least, Kellerhoff has discovered, because he avoided paying much of the tax due on it. A year after coming to power in 1934, he received a demand for 405,494.40 RM, based largely on book earnings. But he never paid and the following year, was struck from the tax records altogether. “No one has so far been able to discover what happened to the tax man who was bold enough to send him that demand,” said Kellerhoff.

• This article was amended on 5 November 2015 to remove an unsubstantiated claim that Mein Kampf is a bestseller in Arab countries.