XML Deserialization : from xmlString to complex class

This is the xml what I get from database:

> <Library>
>     <Header>
>         <HeaderID>01</HeaderID>
>     </Header>
>     <Books>
>         <Book>
>             <Name>Book1</Name>
>             <Category>Fiction</Category>
>             <Authors>2</Authors>
>         </Book>
>         <Book>
>             <Name>Book2</Name>
>             <Category>Non - Fiction</Category>
>             <Authors>1</Authors>
>         </Book>
>      </Books>
>      <Authors>
>           <Author>
>               <Name>Author1ForBook1</Name>
>           </Author>
>           <Author>
>               <Name>Author2ForBook1</Name>
>           </Author>
>           <Author>
>               <Name>Author1ForBook2</Name>
>           </Author>
>       </Authors> 
></Library>

This is my class:

public class Library
{
   public Header header{get; set;}
   public List<Book> books{get;set;}
   public List<Author> authors{get;set;}
}

public class Header
{
   int ID{get;set;}
}

public class Book
{
  string Name{get; set;}
  string Category{get; set;}
  string Fiction{get; set;}
}

public class Author
{
  string Name{get;set;}
}

What I want to be able to do is, to deserialize the xml string I get from database into the class object - Library. Currently I am using the following code to it, but I get an error:

String xData = RequestXml;
XmlSerializer x = new XmlSerializer(typeof(Library));
Library myTest = (Library)x.Deserialize(new StringReader(xData));

The error I get is:

There is an error in XML document (1, 2).

Please help me resolve this issue.