Why is it important to research the author before reading the book?

It is important to research an author before reading a book, for example, if you are reading a political book, then most times the author is biased towards one person over another.

The author usually writes a book based off of their knowledge and understanding.

An author often writes from he or she knows. So by researching the author he may understand more about the characters, may understand the main idea, bias, ect.