Reading XML documents using LINQ

<?xml version="1.0" encoding="utf-8" ?>
<Books>
  <Book>
    <Subject>
      Social Science
    </Subject>
    <Content>
      History,Geography
    </Content>
  </Book>
 
  <Book>
    <Subject>
     General Science
    </Subject>
    <Content>
      Biology,Chemistry,Physics
    </Content>
  </Book>
  </Books>

var books = from nodes in System.Xml.Linq.XElement.Load("Books.xml").Elements("Book") select nodes;
 
            if (books != null)
            {
                foreach (var b in books)
                {
                    listBox1.Items.Add(b.Element("Subject").Value.Trim());
 
                }
            }