My observations are rooted in what I see around me in the dilution and seduction of the larger ‘Christian’ culture. ‘Christian’ bookstores abound with bad theology, secular self-help books and down right bad philosophy designed to tickle people that do not seem to desire the only tested, true and Scriptural path to enlightenment - loss of self and sacrifice.
That said, what I have learned about ‘The Shack’ I have learned from those around me. Almost without exception, the folks that claim to find great insight or help from this book have been people who, by in large, generally shun the elemental ethic of sacrifice and denial called for in Scripture for our basic walk. This departure in the lives of most advocates (so far) stands as an alarming criticism on its own. I have discussed the book several times now with others and have come away with no other conclusions than those I hold here.
To your credit, those in the ‘pro’ camp all hold to the same basic view that you have presented - allegorical illustration of greater truth. Knowing several who have read the book and hold the views of Colson, myself and others on this post, we ask: Why - what is so profound that we do not find this already in Christ alone? Clearly, some of the imagery chosen in the book and some of the words presented do, indeed, undermine and blur sound doctrine. For understanding and enlightenment, we have already been clearly presented with the true source of all revelation - if we ask and seek.
For all of these reasons, and many more, I prefer to choose the real thing.
Of course, Scripture is sufficient and there is nothing we need that we we do not find in Christ. Having said that, sometimes a vivid metaphor can intensify our understanding of things we find in Scripture.
For example, the Narnia Chronicles (focusing on The Last Battle, for example) do not contain new revelation about heaven or anything else for that matter but The Last Battle made heaven seem real to me. I's a matter of focused intense metaphor, I think.
In the case of The Shack, Young deals with how to understand God's love in the face of intense suffering and disappointment. I don't think I fit into the category of "people who, by in large, generally shun the elemental ethic of sacrifice and denial called for in Scripture for our basic walk" and the author doesn't either.