I've always thought of Eden as perfection, but Guthrie describes it as potential. Adam and Eve were sinless but not yet glorious. Thus, what we will inherit now since Jesus came, died, and was raised to life and glorified, is even better. We, too, will be raised and glorified, and there will be no possible way sin could come in and distort.
Guthrie does a great job of surveying the entire story of the Bible from Eden to the New Jerusalem, making it a great book for personal growth as every Christian needs to understand the storyline of scripture. It's also a great book for a small group since it includes discussion questions at the end of the book.