This review will contain spoilers!
In many sentences:
Let me first say that as someone who knows nothing about Paradise Lost, or even epic poetry, this was an interesting, engaging, and approachable book. I never once felt lost or confused , even as Lewis got into the more detailed aspects of the poem. It cannot be understated how great Lewis is at taking a complicated or difficult to grasp idea, and putting it to terms that are simple and easy to understand.
For example, on page 84 he writes "Since the whole point of Adam's remark is that the approval of the will alone makes a mind evil and that the presence of evil as an object of thought does not - and since our own common sense tells us that we no more become by bad thinking of badness than we become triangular by thinking about triangles - this passage is wholly inadequate to support the astonishing doctrine attributed to Milton."
With that said, I can't say for sure yet, that this book will accomplish what it sets out to do - namely to provide the reader of Paradise Lost with the tools and information necessary to engage and enjoy it as it was meant to be appreciated. I think it will, and I am certainly looking forward to reading Paradise Lost, but until I actually do it's difficult to say if it will succeed as well as I anticipate it to. I can say, though, that it has helped me not be as intimidated by the work as I once was.
For now, I happily recommend A Preface to Paradise Lost to anyone who enjoys reading about literature, or who is planning to read Paradise Lost. It's entertaining even without reading Paradise Lost, so I can only imagine my appreciation for it will increase once I get around to reading it.
C.S. Lewis the Last Line of in A Preface to Paradise Lost