In the text, it says that it was the middle of spring, and it was just past midnight, around 1 am. We also know from the beginning that Montresor is planning to do something to Fortunato. This lures the reader in to want to know what Fortunato will do.
As Montresor lead Fortunato to the vault of his palace, there are skeletons of past members of his family laying there, setting up a dark mood. The entices the reader into wanting to find out why the skeletons are there and what is Montresor's plan for revenge.
Montresor, once in the vault, gives Fortunato even more wine on top of the ones that he had already drunk, as well as promising the Amontillado. The reader probably has an idea of what Montresor is doing, but still doesn't know his plan for revenge. This makes the reader want to continue reading.
Montresor had brought Fortunato towards the "vault," and preceded to lock him off in the vault, where he had promsied to give him the Amontillado
As Monstresor had finished his plan of revenge, we hear Fortunato's final words, a call for help. The reader now knows the final lan, but has remaining questions, such as if Montresor had ever gotten caught?
Montresor had never been caught for being the reason Fortunato had died. For half a centruy, and no one had found his body or bones down in the vault.