In the case of Dark Eden, reality seemed so skewed, even the normal aspects of the world didn't fit. Relationships were shallow, dialogue was unrealistic, and the characters were poorly developed... even that of the main character, who we are supposed to care about the most. I found myself not caring at all: was not concerned when the kids' worst fears were faced, because at the end things just didn't make sense. And the ending! Don't get me started. What a cop out.
I walked away from this one most gladly... but not until discovering one very important thing: one of my greatest fears is having to face another book as poorly-written as Dark Eden.