fiction
If you're reading fiction searching to know the depths of God, you're looking in the wrong place. While books like The Da Vinci Code and The Shack may contain what the writers believe to be theological and empirical truth, they are fiction. Read them as such. I haven't read The Shack yet, but will be doing so in late June, and I couldn't put The Da Vinci Code down (or any of his other books). Do I believe that there was a cult where Jesus had sex with Mary? Not so much, but Dan Brown is an incredibly gifted and entertaining fiction writer.
Common grace, though, can run rampant through them (maybe not Da Vinci...). Instead of just labeling a book as "crap," especially if it's fiction, let's just read it through a Scriptural lens and keep our opinions of the theology of a fiction book to ourselves. It's fiction...if William Young or Dan Brown start writing "theological" books, then we'll critique them as such. I think these attitudes are exemplary of how many conservative Christians act, and thus are part of the reason that Christianity is so divided (e.g. all the denominations).