The arguments in Forged are nothing new. Christians have long known that some of the texts are not by the attributed authors. Eusebius made the same points and cited competing views more than 1600 years ago in his History of the Church.
For example, I seem to recall that Eusebius took issue with the book of Revelation being attributed to the Apostle John.
Here is some stuff I found online from his work.
Ecclesiastical History, Book 3, Chapter 3 .—The Epistles of the Apostles.
1. One epistle of Peter, that called the first, is acknowledged as genuine. 1 And this the ancient elders 2 used freely in their own writings as an undisputed work. 3 But we have learned that his extant second Epistle does not belong to the canon; 4 yet, as it has appeared profitable to many, it has been used with the other Scriptures.
5. Paul’s fourteen epistles are well known and undisputed. 16 It is not indeed right to overlook the fact that some have rejected the Epistle to the Hebrews, 17 saying that it is disputed 18 by the church of Rome, on the ground that it was not written by Paul. But what has been said concerning this epistle by those who lived before our time I shall quote in the proper place. 19 In regard to the so-called Acts of Paul, 20 I have not found them among the undisputed writings.
