Add a new book to an existing xml file.

Question

I have a xml with books that looks like this:

<Books>

  <Book1>

    <Title>title1</Title>

    <Author>author1</Author>

    <Price>20</Price>

  </Book1>

  <Book2>

    <Title>title2</Title>

    <Author>author2</Author>

    <Price>15</Price>

  </Book2>

</Books>

And i want to add a new book to the list.
What is the proper way to do that?
Thx