The reason for this exception is because an error with connection string you prepare.
modify your connection string preparation like this
OleDbConnectionStringBuilder sb = OleDbConnectionStringBuilder ();
sb.Add("Jet OLEDB:Database Password", "*******");
sb.Add("Jet OLEDB:System Database",sfd.FileName);
bookConn = new OleDbConnection(sb.ConnectionString);
You can also refer here
] to know more about connection string preparations. &building-better-connectionstrings-with-connectionstringbuilder/