What happens next vs What's happening

Every story teller starting before Homer found a way to sustain the reader's interest. The author might think of this as suspense (Will Phileas Fogg get around the world in 80 days?), or mystery (Who dunit?), or story arc (What will happen to Tom Sawyer after he paints the fence?). The driving force might characters (Jane Austen) or the plot (Jules Verne) or even setting (J.R.R. Tolkien). While the choices are seemingly endless, every writer most find a way to keep the pages turning.

One way or another, the reader is driven forward by What happens next? We may wonder about the fate Pip or Jurassic Park or Middle Earth. Almost any technique is acceptable . . .

except one: What's happening?

The characters may be confused (Elizabeth Bennet in Pride and Prejudice) or and reader may be misled (red herrings), but the reader can never simply be confused.

If the reader is asking What's happening? instead of What happens next? the writer has failed and most readers will simply discard the book. Reader's will tolerate many kind of puzzles, except the one asking what is happening in this story?