Dr. Wayne Martindale is a recognized authority on the works of C.S. Lewis. That said, I never felt that I was being lectured to or spoken down to as I read this book—though I now know that I need to read a LOT more Lewis.
The purpose of the book is to look at various myths of both Heaven and Hell, and compare them with the pictures of both that Lewis paints in his works. Martindale shows that Lewis' ideas of the afterlife are far more Scriptural than most of the common misconceptions that we have today.
I think that the richest parts of this book are those sections where Martindale explores in depth Lewis' conceptions of heaven and hell. These read like literary criticism, but they are easilly accessible to any reader. Readers who are familiar with Lewis' writing will want to explore them again, and those of us who have not read as much of Lewis as we should (or would like) will find ourselves buying more books!
One of the things that I was hoping to gain from this book is an explanation of Lewis' alleged heterodoxy. I've heard him accused of universalism. I've heard that he believed in Purgatory. From reading Mere Christianity, I can tell he was fairly ecumenical. Martindale defends Lewis from the first two charges in this work.
Much of Martindale's book is literary criticism: he looks closely at the symbols and imagery that Lewis uses, and shows their meaning in terms of Heaven and Hell. He assumes that the reader has at least a passing familiarity with Lewis' work, which I am increasingly aware that I do not have. The Space Trilogy is referenced many times—I have put reading that trilogy at the top of my must-read list. I've decided that I really need to start reading more C.S. Lewis—the weekly readings out of Mere Christianity aren't enough. And I'm buying the Narnia set to read to my daughter.