Here are some great books on parenting — some are general parenting guides and some are specific to twins.
They are in no particular order — actually, they’re in the order in which they popped into my head
(so psychological profiles of me can begin here)

Parenting Beyond Pink & Blue: How to Raise Your Kids Free of Gender Stereotypes by Christia Spears Brown

Peaceful Parent, Happy Kids: How to Stop Yelling and Start Connecting by Dr. Laura Markham

Nonviolent Communication: A Language of Life: Life-Changing Tools for Healthy Relationships by Marshall Rosenberg

Emotionally Healthy Twins: A New Philosophy for Parenting Two Unique Children by Joan Friedman

The Sister Knot: Why We Fight, Why We’re Jealous, and Why We’ll Love Each Other No Matter What by Dr. Terri Apter 

Ask the Children: What America’s Children Really Think About Working Parents by Ellen Galinsky

Why Have Kids: A New Mom Explores the Truth About Parenting and Happiness by Jessica Valenti

All Joy and No Fun: The Paradox of Modern Parenthood by Jennifer Senior

Mom Still Likes You Best: The Unfinished Business Between Siblings by Jane Isay

The Sibling Effect: What the Bonds Among Brothers and Sisters Reveal About Us
by Jeffrey Kluger