From a thoughtful (Catholic) friend:

Re Revelation, I have taught on this book a number of times, and though it needs supplementing, there is a book (written before 1990’s) which one really can’t go past for getting a level handle on it: Michael Wilcock “I Saw Heaven Opened”. What I really find useful about this book is its suggested “structure” of seeing the book of Revelation as eight scenes of seven scenes each. It sounds contrived, but it really works better than any other suggested structural analysis of the book that I have ever come across. It is simple for first time readers too.