Regina has an excellent discussion about the importance of the ‘gap’. Where something isn’t quite explained enough or isn’t explained at all. Even in very easy to understand stories there are gaps (how did the character get from their home to the hotel?), but gaps are fundamental. One measure of how sophisticated a work is simply in how large (or vague) the gaps are. Poetry is more ‘gappy’ than prose, and James Joyce is more ‘gappy’ than Bryce Courtenay.