The Power of Habit, by Charles Huhigg
A great resource for anyone wanting to change a habit. It is thorough and well researched.
The Feeling Good Handbook, by David D. Burns, M.D.
One of the best books for understanding how our thinking shapes our behavior.
How to Talk so Kids Will Listen, and Listen so Kids Will Talk, by Adele Faber and Elaine Mazlish
A treasure.