After breaking the news almost exactly a year ago, I finally got around to seeing the first Spider-Man original art by Steve Ditko in Amazing Fantasy #15.
The art was lovely, but it was somewhat anti-climactic since I'd read the story literally hundreds of times. Foolish, I know. There's a small bit of new information to be gleaned from the artwork, where Stan Lee asked for changes, but Ditko followed his pencils very closely so there's not a lot of underlying drawing.
The entire comic book art is there, so there are three other stories with Ditko art that aren't seen nearly as often.
I really can't think of any better home for this than the Library. Lee and Ditko's creation has become an American icon over almost 50 years now. More pictures are here.