The author's manner of writing is called the writing style. The writing style is the ways by which the author chooses to express his ideas, feelings and himself/herself. The writing style is unique to all writers, just like everyone is unique so do with their writing styles. Usually, the style of the author affects the acceptance, understanding or the feedback from the readers or the listeners. The writing style in a certain paper or essay is expected to be consistent in order not to distract the reader's focus on the sudden switching of style.
(Source: Google)
Hope that helps! =D