Books that are scary because of their length:
The Book Thief by Markus Zusak
The Vampire Academy Series by Richelle Mead
Reached by Ally Condie
Partials by Dan Wells
The Casual Vacancy by JK Rowling
And the ones that have pretty heavy duty content that sometimes I just don't think I can handle:
The Kite Runner by Khaled Hosseini
This is one of the few Adult books that I read - and it did make me cry.
Perfect by Ellen Hopkins
Be prepared - I guess every Hopkins book will weigh you down. But then again, she also manages to save you from yourself. If needed.
Tempest by Julie Cross
This one is not particularly said, it's just complicated. Time travel almost always results in my brain knotting itself into weird twists!