Answer: The editor likes your work, or she surely wouldn't have taken up valuable time to write to you. It's so easy to reach for those pre-printed slips. Returning manuscripts is an unpleasant aspect of any editor's existence and most take the easy way out.
An opening hook is one that promises action-to-come to the reader, and it's usually attached to, or very near, the transition. The opening hook near the first line of a novel, should reflect the central problem that will challenge the protagonist of the story. There should be an opening hook in each scene, but none are so important as the first one in your book or short story.
One of my teachers sneered at hooks, saying they are the stuff of "hacks" and "pulp fiction" and had nothing to do with literature. I disagreed and was told to shut up, so maybe I'll sound off a bit here.
It's true, that hooks can be clumsily used by writers who still have to hone their skills. But just for the sport of it, lets take a look at some first lines of novels from authors with undeniable skill:
Charles Dickens: A Tale of Two Cities. "It was the best of times; it was the worst of times." This sentence certainly is a hook and a promise of action. The story is about the French Revolution.
Jane Austin: Sense and Sensibility. "The family of Dashwood had long been settled in Sussex."
The story is about the Dashwood family having fallen on hard times and the key word (hook) in the transition is "had"....
Alexander DuMas (pere): The Count of Monte Cristo. "On the 24th of February, 1815, the look-out at Notre-Dame de la Garde signaled the three-master, the Pharaon from Smyrna, Trieste, and Naples. As usual, a pilot put off immediately, and rounding the Chateau d'If, got on board the vessel between Cape Morgion and Rion island."
One may be justified in saying that there is no "hook" here, beyond the arrival of a ship and the inevitable fact that an assumed "someone" will arrive on it. Yet the story of Edmund Dante (who does arrive on the Pharon) is one of a man imprisoned in the Chateau D'If, and who later escapes, then has his fortunes change, making him extremely rich (through his many adventures upon the sea), until he reappears one day in Marseilles as the wealthy "Count."
Time has not labeled any of the above writers "hacks," though Dickens was pretty much considered one while he yet lived.
What do readers think? Are opening hooks important? Should they make a promise to the reader?