private void init()
        {
            System.Threading.Thread.Sleep(1000);
            SelectEpubWindow dialog = new SelectEpubWindow();

            dialog.Show();
            this.Owner = dialog;
            this.Close();
        }
 //電子書籍一覧の画面に戻る
 private void indexButton_Click(object sender, RoutedEventArgs e)
 {
     SelectEpubWindow dialog = new SelectEpubWindow();
     dialog.Show();
 }