The reason Calvin didn’t preach Revelation isn’t exactly what Gerald Bray addresses on pages 51–52 in God Is Love, but what he says there probably takes us into the vicinity of the answer to that question:
The book of Revelation is in a category all its own and has frequently been misunderstood. One of the real advances in twentieth-century biblical scholarship was its rediscovery of the genre of apocalyptic literature, which has made it easier to interpret the last book of the Bible and to justify its place in the canon. For many centuries, Revelation was either ignored or misunderstood because no one really knew what to do with its rich symbolism. Many made the mistake of treating it as a literal prophecy, which led to fantastic predictions of the imminent end of time, and so on. Invariably, readings of that kind would turn out to be wrong, and that discredited the book in the eyes of many serious scholars. Now, however, it is possible to appreciate the text of Revelation for what it is and to realize that it is one of the most profoundly theological books in the entire Bible. It may take some time for awareness of this to percolate down to the average churchgoer, who is still liable to be misled by sensational interpretations, but there is a new scholarly consensus on the subject that promises to enhance, not diminish, the book’s reputation and usefulness in the life of the church.
Revelation is in the Bible, inspired by God, for the benefit of his people. These realities keep me from feeling any consternation about having attempted a book on which Calvin didn’t comment. Still, historical perspective is always appreciated.