To engage your reader, especially in today's world filled with distractions, you must keep your story exciting. Excitement is created through dramatic action where a positive outcome for the protagonist is constantly threatened.
Without gorgeous writing, exciting action and/or compelling characters (preferably all three), a reader's mind wanders. A reader with a wandering mind detaches from the story, puts down the book and later, if she does pick the story up again, she'll not recognize where she left off because, though her eyes skimmed the words the first time, meaning didn't penetrate.
Because she has to go back to find where she last remembered reading consciously, any true connection to the story has been compromised and the reader may never fully commit to finishing your story.
Find a scene, passage, chapter, section that's boring to you? You can be sure the reader became bored even earlier in the story than you did. Now, rewrite the scene using extreme ideas, wild choices, any surprising elements you can pull in to create emotion and excitement, tension, heart and conflict. Brainstorm for all possible ideas to create more conflict and excitement and then hone them to fit your story.
Today I write.
For more: Read my Plot Whisperer and Blockbuster Plots books for writers.