The Picture of Dorian Gray is another classic that I've read again and again. I suppose you could even count this book to be in the 'magical realism' genre (one that I adore) due to it being so realistic, and yet, there is the whole idea of a picture ageing where the man doesn't.
Still, I believe that Wilde was trying to tell us more about humanity and cruelty rather than what immortality would taste like.
I can't really explain why I adore this book so. Part of it is due to the Wilde's writing style and his characters but a lot is also based on the issues that he raises (what with romance, and human cruelty and our truer, baser natures, etc).
Wilde wove a magical atmosphere wrought with some of the darker parts of our natures that just spoke to something in me. It's definitely worth reading, if only for the freaky scenes where Dorian Gray figures out what happened to him!