I only read Frankenstein last year (and my passive vocabulary is ridiculously broad, anyway, so it wouldn't have mattered much had I read it earlier), so I only found it dreadfully boring and predictable, but I had a similar experience to YamiRaziel's when I was given The Great Gatsby as a reward for winning an English language contest in 7th grade. (Whoever thought that was an age-appropriate novel? I was 13 at the time...)
I did not get The Great Gatsby. At all. To be honest, I still don't get what the fuss is about with this one, since I also find it dreadfully boring. Somehow, "classics" about white dudes doing dude-things, told from the POV of white dudes, do nothing for me. At least Dracula has female POV characters...
"... And the lord set a mark upon Caine lest any finding him should kill him and the mark was ..."