I haven’t read the book, so you’ll get a better answer from someone who has.
The author Bart Ehrman, apparently a former evangelical, now calls himself a “happy agnostic.” His field of study is apparently textual criticism of the scriptures. And the book is about textual analysis of the NT, especially with regard to the number and history of manuscripts, and possible errors made in transcribing the texts during the many hundreds of years before the invention of the printing press.
I would guess that it’s not something that has to be a threat to your faith. But there are many people to whom I suspect it would be a threat, simply because they tend to have doubts aroused by such things.
For Catholics, who have confidence that the deposit of Faith has been accurately handed down to us even in the absence of writings, I would think that this would be less of a concern. Also, in an interview I read, the interviewer posed a question as to whether he thought some people might get the impression from the book that the bible is much less reliable than they had thought. He said that could be an outcome, although that was not his thesis or intent.
In the same interview, I got the impression that he treated such people as the Marcionites, Ebionites, and Gnostics as more or less equal contenders for the ‘official’ version of Christianity, but who happened to have lost out to what he calls the “Proto-Orthodox”–people like Ignatius of Antioch and Tertullian. Strange. I always thought those people were Catholic!