There are tons of books that make me think, but the ones that stick with me are ones I recommend to people. The following books deal really well with hard topics. Most of them are sad, heartbreaking books but they also have a glimmer of hope.
13 Reasons Why: Could someone have helped her?
Wintergirls: So haunting
Purge: Realistic yet humorous
Life After - Heartbreaking, but eye opening too
Speak - I love how she found her courage
Life as We Knew It - makes me want to stock up on canned goods whenever I hear about a potential natural disaster.
Keep Holding On: Heartbreaking, but hopeful
Can't Get There from Here - I liked the librarian in this one
Fat Cat: I loved the blend of science with food