The Shack is one of those books that you either love or hate. I, for one, loved it.
The biggest issue that the "hate it" crowd seems to have are theological in nature. (i.e. that it doesn't fit into their theological box).
The "love it" crowd, usually point out that it is fiction and somewhat of a parable, and is intended to provoke discussion and make one think, not to teach matters of doctrine.
Well, I'm different. (Shock!) I neither loved it nor hated it. Here's my review: