They cover every aspect of human behavior to give you excellent relationship information. They also offer practical advice on changing your life for the better:
Emotional Intelligence by Daniel Goleman
Sex on the Brain by Deborah Blum
Getting the Love You Want by Harville Hendrix
The Male Ego by Willard Gaylin, M.D.
The Nurture Assumption by Judith Rich Harris
The Blank Slate by Steven Pinker