It was written as an introduction and is very successful as such. It is not a thorough commentary of Revelation. If you have never studied Revelation this is a great place to start.
At the time this book had not been published but I was able to get some tapes by Poythress, and they taught what is written in this book. When the book came out I got it right away and I have to say that I was not disappointed in the tapes or in this book.
Poythress writes like a kindly, wise elder. I say he is kind because, though he takes a position on the interpretation of the book, he is gracious to those who disagree with him. One of the things I particularly liked about this book is his discussion of how to outline the book. He listed a few different ways that this could be outlined, but rather than attacking various positions he affirmed that the existence of these differing views should cause us to marvel at the greatness of God in the book. These things show that the book of Revelation is like a giant tapestry, with many colors and patterns weaving in and out. The book is so rich that one can never tire of admiring the beauties of God in it.
As to his position, Poythress says that the book follows the pattern of recapitulation - it describes the same historical events over and over again using different metaphors and pictures. So, rather than being a straight chronological description of the end time, the book of Revelation describes the second coming, and the events surrounding it, several times.
Poythress shows that the book of Revelation is actually comprised of several cycles of judgment. He gives the tools for understanding how to identify these cycles and in doing so makes Revelation slightly less difficult.
This is the place to start in understanding the book of Revelation.