The book of Revelation was called, until relatively recently, the Apocalypse, or the Apocalypse of St. John. Although the author identifies himself as John, it is Tradition which says that the author is St. John the apostle.
Here is commentary from St. Victorinus, who lived in the late 200's, and was Bishop of Pettau:
1-6."There came one of the seven angels, which have the seven bowls, and spoke with me, saying, Come, I will show you the judgment of that great whore who sits upon many waters. And I saw the woman drunk with the blood of the saints, and with the blood of the martyrs."The decrees of that senate are always accomplished against all, contrary to the preaching of the true faith; and now already mercy being cast aside, itself here gave the decree among all nations.
Apocalypse 17:3"-->3."And I saw the woman herself sitting upon the scarlet-coloured beast, full of names of blasphemy."] But to sit upon the scarlet beast, the author of murders, is the image of the devil. Where also is treated of his captivity, concerning which we have fully considered. I remember, indeed, that this is called Babylon also in the Apocalypse, on account of confusion; and in Isaiah also; and Ezekiel called it Sodom. In fine, if you compare what is said against Sodom, and what Isaiah says against Babylon, and what the Apocalypse says, you will find that they are all one.
Apocalypse 16:9"-->9."The seven heads are the seven hills, on which the woman sits."] That is, the city of Rome.
Apocalypse 17:10"-->10."And there are seven kings: five have fallen, and one is, and the other is not yet come; and when he is come, he will be for a shorttime."] The time must be understood in which the written Apocalypse was published, since then reigned Cæsar Domitian; but before him had been Titus his brother, and Vespasian, Otho, Vitellius, and Galba. These are the five who have fallen. One remains, under whom the Apocalypse was written— Domitian, to wit."The other has not yet come,"speaks of Nerva;"and when he is come, he will be for a short time,"for he did not complete the period of two years.
11."And the beast which you saw is of the seven."] Since before those kings Nero reigned.
"And he is the eighth."] He says only when this beast shall come, reckon it the eighth place, since in that is the completion. He added:—
"And shall go into perdition."] For that ten kings received royal power when he shall move from the east, he says. He shall be sent from the city of Rome with his armies. And Daniel sets forth the ten horns and the ten diadems. And that these are eradicated from the former ones,— that is, that three of the principal leaders are killed by Antichrist: that the other seven give him Honour and wisdom and power, of whom he says:—
Apocalypse 17:16"-->16."These shall hate the whore, to wit, the city, and shall burn her flesh with fire."] Now that one of the heads was, as it were, slain to death, and that the stroke of his death was directed, he speaks of Nero. For it is plain that when the cavalry sent by the senate was pursuing him, he himself cut his throat. Him therefore, when raised up, God will send as a worthy king, but worthy in such a way as the Jews merited.
This lecture from St. Cyril of Jerusalem ties together many of the apocalyptic books of the Bible. It isn't strictly on Revelation, but he did write in the 300's.
If you scroll way, waaay down at Catholic Encyclopedia, their article gives the same interpretation as St. Victorinus, which is that the Whore of Babylon is the Roman Empire.