@Override
	public Book readBook(String isbn) {
		if (doc == null)
			return null;

		Element currRoot = doc.getRootElement();
		Element parrentBook = currRoot.getChild("books");
		List<Element> listBooks = parrentBook.getChildren();

		for (Element book : listBooks) {
			String bookIsbn = book.getChild("isbn").getText();
			if (isbn.equals(bookIsbn)) {
				String title = book.getChild("title").getText();
				String author = book.getChild("author").getText();
				double price = Double.parseDouble(book.getChild("price")
						.getText());

				Book bo = new Book(bookIsbn, title, author, price);
				return bo;
			}
		}
		return null;
	}