Puritan plain style refers to a style of literature widely used by Puritan writers. The works written in this style are simple works, without the use of figure and fantasy language. Moreover, this type of literature presents works with a simple and straightforward language, are short, informative and without much ornamentation and mirabolating things. Puritan writers used to write direct prose using everyday language, these two elements being two striking features of this style.
Because his father has been ordered to relocate on the orders of the Fury (the Fuhrer, Adolph Hitler). Essentially, Bruno's father has been promoted to a Commandant position at Auschwitz, and this is why the family has to leave their house in Berlin.