For people into psychology:
Sybil by Flora Rheta Schreiber

For people into futuristic philosophy:
Fahrenheit 451 by Ray Bradbury

For people into historical fiction:
Hang a Thousand Tress with Ribbons by Ann Rinaldi

or...

Roll of Thunder Hear My Cry by Mildred D. Taylor (Mostly Fiction)

For people into plays:
The Importance of Being Ernest by Oscar Wilde