Maybe this is because the book is a mirror that each reader holds up to the text.

What does the author mean by this sentence?

The meaning of the novel changes depending upon the perspective of the reader.

The writing in the novel is smooth and transparent, like the surface of a mirror.

When a reader finishes this novel, he or she will reflect upon its meaning.

The author uses the symbolism of glass and mirrors throughout the novel.

The meaning of the novel changes depending upon the perspective of the reader.

Explanation:

This is the best explanation of the statement. When the author states that the book is a mirror for each reader, what it means is that each person reflects a little of his own person upon the book. Therefore, the meaning of the novel changes depending upon the perspective of the reader. This is an important factor to take into account when interpreting a text.

The meaning of the novel changes depending upon the perspective of the reader

Explanation:

I think this is because each persons refliction is different, so they would see the text in different ways.