Doesn’t this fall under the prohibition of the Sages regarding heretical books?

It does fall under it (this is not a rabbinic decree, but a Torah-level prohibition of “and you shall not stray after”). But involvement of this kind with heretical books is, in my opinion, not prohibited.

The New Testament (and especially the “Gospels”) does not explain Christian theology (the “Holy Trinity,” for example), which developed later.
Someone who reads the Gospels without the later interpretations sees Jesus as a kind of guru, a savior of the downtrodden, a fighter for justice, and someone who challenged the establishment.
There is in the book an anti-rabbinic, anti-Pharisaic message, a moral-humanistic message, and a somewhat anti-halakhic one (such as his permission to heal on the Sabbath). But beyond that, there is no “heresy,” idolatry, and the like in the book.
Jesus and his first disciples were Jews who observed the commandments, and all the later theology does not emerge from a straightforward reading of the book.
In my opinion it is recommended to read it, in order to know history, to become familiar with the spirit of the period, and the background to the growth of such sects.
His claims also come up nowadays (such as: the rabbis are only looking for money and honor, rabbinic Jewish law is too formalistic, it does not see human needs and does not take religious feeling and experience into account). What has been will be.

In summary—if the problem is only with reading books of idolatry, then in my opinion, even if formally the book belongs to that genre, essentially it does not.

It is דווקא these claims that I do not agree with. Even a tree or a statue is not idolatry in its content. It receives the halakhic status of idolatry because of people’s attitude toward it. Today the New Testament is a sacred object among Christians, and assuming they are idol worshipers, this too receives the status of an object of idolatry.
And still, as I wrote, there is room to permit it for the above purposes.

Thank you for the response, but it is novel in my eyes.

After all, the New Testament is not a physical object (by the way, I downloaded it from the internet, so I did not even read it from a book). And I myself do not relate to it as describing idolatry, since I do not believe at all in the miracles described in it.

So in the Rabbi’s opinion, can abstract material (a literary work) be an “object of idolatry”?

Hello Rabbi, from where does your assumption arise that the Torah prohibition “do not stray after” refers subjectively to the manner of study, and does not forbid any use of the prohibited object? (Today the consensus is that one should burn the book, including the Hebrew Bible, which suggests an all-encompassing attitude toward any engagement with the book.)

Noam, see the Rabbi’s view here:

https://mikyab.net/%D7%A9%D7%95%D7%AA/%D7%90%D7%99%D7%A1%D7%95%D7%A8-%D7%9C%D7%99%D7%9E%D7%95%D7%93-%D7%A2%D7%96/

Aharon,
If it is not a book, then indeed there is no object here. A file is not an object. But the prohibition on reading heretical books still stands. And its definition as a heretical book depends on what its believers see in it, and not necessarily on what is actually in it. Exactly like wood and stone in relation to idolatry.