Here's an interesting excerpt from Forged by Bart Ehrman (pay particular attention to the last sentence):
"A number of the books of the New Testament were disputed already in early Christianity, among the Christian scholars of the second to the fourth centuries, who were arguing over which books should be included in Scripture.
The most famous instance is the book of Revelation. A third-century Christian scholar of Alexandria, Egypt, named Dionysius, argued that the book was not actually written by Jesus’s disciple John, the son of Zebedee. Dionysius’s argument was compelling and continues to be compelling to scholars today. He maintained that the writing style of the book is so different from that of the Gospel of John that they could not have been written by the same person (modern scholars differ from Dionysius only in thinking that the Gospel too was probably not written by John). Dionysius thought there must have been two authors of the same name who later came to be confused as the same person. But it is interesting that Dionysius, according to the church father Eusebius, had a number of predecessors who had argued that Revelation was written not by a different man named John, but by a heretic named Cerinthus, who forged the account in order to promote his false teaching that there would be a literal future paradise of a thousand years here on earth."