I was surprised because as a reader I was unprepared for this ending.
In Part IV of the story, the narrators mention having seen Miss Emily "purchase a man's toilet set in silver with the letter H. B. on each piece, and she bought a complete outfit of men's clothing, including a nightshirt and we said, 'They are married." These narrators, then, are "not surprised" when Homer Barron is gone the first time because the streets have been finished and the assumption is made that he has returned to the North to prepare for Emily's arrival. Three days later, Barron does return to town. So, when Homer again is not seen and Emily appears alone in the windows and does not leave her house for months, again the townspeople "are not surprised."
With the narrators' explanations of events and their saying "we were not surprised," the reader tends to accept this assessment of events. And, when the "Negro" continues "going in and out with the market basket" and the old routine of Emily's life is apparently restored, the reader is not prepared for the horrific ending. Even though Faulkner hints at Emily's abnormalities--"perverse"-- he distracts the reader with other words such as "impervious, dear, and tranquil" in describing her.
Having been raised as a lady in the tradition of the Old South, Emily's having committed murder seems out of character, as well--much like the shock the viewer has when learning that the genteel, "dear and tranquil" aunts have been giving their guests poison in "Arsenic and Old Lace."
I was supprised by the ending. However, i feel very sorry for Emily. The townspeople (ladies, old men, ect..) and her father were crazy, not Emily. How could they expect her to get married with a noble while her family was the last noble in the town. Obviously they forced her to live alone. Emily was human being and she had the right to live, to love. It is undeniable that her act of killing her lover and staying together was terrible. But it was fictitious aspect of literature. It is unreal and our duty is to find our the real one behind it.
Yes and no, I was surprised she was still sleeping next to him, but I was not surprised that she killed him and kept his body there all those years. She was crazy!