A few odd questions

I'm a 15 year old trying to read more classic literature after I went through a phase of just not reading that much.

I'm currently reading Heart of Darkness by Joseph Conrad and really enjoying it, and next in my queue are things like The Trial, Crime and Punishment, The Secret Agent, Oliver Twist, and Down and out in Paris and London. I was wondering if you guys have any other recommendations for me?

Also...I really want to read Frankenstein next but I'm wondering what is the text I should read. 1818 or 1831? I don't mind something more advanced I just want to know which is the better read or more preferred in "academic" circles.