What is an author's style?

Answer 1

The author's style will include point of view, sentence structure, syntax, tone

Here is a good definition.

http://www.readwritethink.org/lesson_images/lesson209/definition_style.pdf

Answer 2

Here are some further sites:

http://en.wikipedia.org/wiki/Writing_style

http://fictionwriting.about.com/od/crafttechnique/g/style.htm

Look particularly at the sites listed at the bottom of each of these.