More interesting however is the fact that the Greek in which the book is wirtten is terrible Greek. I have read that it is utterly dissimilar to the Greek style in the gospel and letters ascribed to John. It's very badly written, utilizing very poor grammer and a much more limited vocabulary than the gospel of John. I have only read this, however. I don't read Greek so I cannot personally vouch for this.
This was known in antiquity by the church fathers, many of whom also knew that there were several different people named John who were important men in the early Church (cf. Papias, who distinguished the John who was "the elder" from the "apostle"; interestingly, Papias was the first to write remarks about Revelation). Here is a remark by Dionysius of Alexandria on the matter:
"In short, when we note all their characteristics it is obvious that the complexion of the Gospel (i.e. John) and the Epistle (i.e. 1 John) is the same. But the Apocalypse (i.e. Revelation) is quite different from these, neither touching nor bordering on any of them, scarcely even having a syllable, so to speak, in common with them. Neither has the Epistle (let alone the Gospel) any remembrance or thought of the Apocalypse, nor the Apocalypse of the Epistle, while Paul by his Epistles gave some hint of his revelations which he did not severally insert. Further, by the diction one can judge the difference of the Gospel and the Epistle from the Apocalypse. For the former are written not only correctly as regards the Greek, but very elegantly in their wording, their reasonings, and the arrangements of their explanations; one is far from finding in them a barbarous word or solecism, or any vulgarism at all. That the other person actually saw a revelation, and received knowledge and prophecy, I will not gainsay. I see, however, that his dialect and language are not accurately Greek, but that he uses barbarous vulgarisms, and in some places actual solecisms. It is not necessary to pick these out now, for it is not in mockery that I have made these remarks, let no one think it, but only to draw out the dissimilarity in the writings" (cited in Eusebius, H.E. 7.25).