One more thing do I actually need to build a mpl::bool_ out of the
is_same function?

No, in fact you can drop the bool, and and true; and just use enable_if. enable_if will even use the boolean operator to get to the underlying boolean ::value so you drop even more syntax:

    template< typename T1
            , typename T2
            >
    void read_data_24( typename enable_if< is_same< T1, T2 > > ::type* /* ptr */ = 0)
    {
        int i = 9;

}

HTH

Steve