I think that Shirley Jackson's "The Lottery" is both a story filled with surprise and horror. I remember reading this story as a high school student and being utterly surprised and horrified at the ending, so much so that I had to go back through and read the story for a second time to see if there were any clues. Jackson's use of foreshadowing is superb, and the subtle word choices she used went unnoticed by me during my first reading, but I picked up on them during my second. The reader does not expect the lottery to be a public stoning. We also don't expect young children to help in the stoning of one of the townspeople. In our society, a lottery is usually a good thing--it brings prosperity to someone. In this society, however, winning the lottery means suffering the ultimate loss--your life. The images Jackson paints in our head at the end of the novel leave us both haunted and horrified. This is why I tend to think of the story has both one of horror and surprise!
I also think it's both horror and surprise. Although there is no graphic description of violence, it is still a kind of Gothic story. There are subtle references to this as a kind of pointless witch hunt, and the social commentary (besides calling to mind ancient ritual sacrifice) could be about Jackson's own time. 1948 - just after WWII, the Holocaust, Atomic Bomb. So, the story could also be a moral tale - a parable.
Besides those examples of Jackson's current (1948) social commentary - if that was perhaps part of what she was doing in the story - the story is about traditional beliefs and ritual: I think these themes lend themselves more toward Gothic and horror since the ritual itself is murder. The surprise is that the lottery "winner" must be sacrificed instead of being given some reward, which is what "lottery" implies. The only possible reward is martyrdom, and that can be a dubious honor especially when we don't even know why the townspeople conduct the lottery in the first place. Simply out of the habit of tradition? The names underscore this symbolism of sacrifice/martyrdom - Mr. Graves and Delacroix (of the cross).
In my mind, it is both.
As you go along reading the story, the town in which it is set seems really pleasant and idyllic. You know there is this lottery going on that causes some amount of argument, but you just assume that it is for a prize or something like that. And then you get to the ending and it is a huge surprise.
But it's not just a surprise, it's horrible too. Once you read the ending, you feel like the whole story was terrible and disturbing. So I really think it is both.
To me the short story "The Lottery" is more of a story that represents irony and surprise. The reader starts out believing that the lottery will be a fun and good thing. Most people fathom that a lottery will produce a reward of some type. When people think about winning a lottery they look forward to being the winner.
The behavior of the people demonstrates that they are excited to be present. They put their names in the box without hesitation. The children frolic and play as they wait for the event to begin. The men chat about farming and their tasks. The reader is led to believe that it will be a good event.
After Tessie's family is narrowed down the reader begins to feel discomfort present. Once Tessie is chosen and revolts against being chosen the reader becomes alerted to the reality of the lottery as being a bad thing.
Tessie's death at the hands of the others as well as the town’s people’s calm return to their duties is a surprise to the readers.