A word to express "removing some parts of history from history books by authorities"

Are you talking about historical revisionism? (Though that word has both neutral and negative connotations).

Bowdlerizing

"Bowdlerized history"

Coined after the work of Thomas Bowdler, who published "The Family Shakspeare."

Revisionism is probably the best, but the verb revise is a neutral term. A common negative verb is whitewashing, which is purposely distorting or hiding the facts (often historical) to make something appear more favorable.

If historical revisionism is not immediately negative enough, then the adjective Orwellian can be added or used. Generally, this conjures the notion of the Ministry of Truth's wholesale reworking of history depicted in 1984; however there is at least one analysis of Orwell/Blair's own politics which identifies him as revisionist (and particularly as a Holocaust denier), so the word has a double impact.

During the Second World War, George Orwell wrote a weekly radio political commentary, designed to counter German and Japanese propaganda in India, that was broadcast over the BBC overseas service. His wartime work for the BBC was a major inspiration for his monumental novel, 1984. Very few readers of 1984 know, for example, that Orwell's attack against the perverse double-talk language called Newspeak was based on the author's revulsion against Basic English, an artificial language that Churchill's wartime cabinet wanted the BBC to use in its overseas propaganda. Similarly, Orwell's model for the lying Ministry of Truth was the British wartime Ministry of Information, which censored BBC broadcasts. The shorthand form, Minitrue, was taken directly from the Ministry of Information telegraphic address, Miniform.

Throughout his lifetime, the great English writer continually questioned all "official" or "accepted" versions of history. As early as 1945, just after the end of the war in Europe, he expressed doubts about the widespread stories of "gas oven" exterminations (Notes on Nationalism). George Orwell was a revisionist. He detested officially sanctioned atrocity and hate propaganda.

Mark Weber, Institute for Historical Review