In "The Oval Portrait" what happens to the narrator when he views the portrait? How does it affect him? At what point might a similar effect (the sublime) be experienced by the reader? What were the reasons the narrator of "The Oval Portrait" was unreliable?

When the narrator moves his candelabra to get a better view of the book he is reading, he "glanced at the painting hurriedly, and then closed [his] eyes."  He does not at first quite understand why he closes his eyes, but he realizes that he needs to assure himself that he is indeed awake and that his vision is not compromised by his delirium or exhaustion.  When he next opens his eyes to view the painting again, he mentions that the painting " at first startling[him], finally confounded, subdued, and appalled [him]."  The narrator does not understand why he is having these conflicting emotions when viewing "an absolute life-likeliness of expression" in the young woman who is portrayed.  Thus, he picks up the book he was reading because it gives histories of the paintings in the house where he is resting.
For the reader of this story, emotions mostly stay in the realm of mystery and suspense throughout the narrative because the reader cannot yet visualize what has struck the viewer of the painting.  It is when Poe finally gives the excerpt from the book describing the painting that the reader might experience the same sublime feelings that the narrator felt.  The excerpt describes how passionate the painter was to portray his lovely bride with such precision.  Again the suspense is drawn out for the reader, waiting for the moment when the painting is finished, and Poe ends with the words "She was dead!"  Thus the reader finally understands not only what the viewer saw, but also the passion behind that portrait. 
In terms of the narrator's reliability, there is the obvious mention of his delirium at the beginning of the story as well as his ill-health that brought him and his valet to take shelter in this abandoned house.  But the reader also notices that, no matter how ill his health, he stays up late reading.  This sleep deprivation could also be an aspect that takes away from his reliability.  He speaks of shadows in the room caused by the candelabra casting shadows in the room and his shifting of the light to see better.  However, the narrator also mentions how careful he is to clear his vision by shutting his eyes and clearing his head before he views the painting again, but this clearance comes with him then viewing the painting for another hour, intensely staring at the painting.  This fixed gaze could also cause him to see things that are not actually there, and his valet is asleep so cannot verify anything in the story.