These are some books that I have found valuable:

Life Stuff
Drama of the Gifted Child - Alice Miller - Great book on how we accommodate to our parents, and how that influences us
Necessary Losses - Judith Viorst - Thoughtful book on the role our past plays in our lives
Emotional Intelligence - Daniel Goleman - The role of emotions and our relationship with them
The Depression Book: Being Present in the Darkness - Cheri Huber - Excellent, humorously written book with the view that depression does not need to be something to fear or hate
Raising Your Right Hand Against Fear - Sheldon Kopp - Thoughtful book on handling anxiety
When Things Fall Apart - Pema Chodron - Beautiful, simple practices for wisdom in daily life

Relationships
The Two Step: The Dance Toward Intimacy - Eileen McCann - Funny, brilliant, cartoon version of extremely typical relationship patterns
Journey of the Heart - John Welwood - Profound insights into the nature of relationships
If the Buddha Dated - Charlotte Kasl - Terrific, basic ideas to keep in mind when looking for a partner
Can Love Last - Stephen Mitchell - Fascinating account of the possibilities of long-term relationships

Buddhist Psychology - All excellent books on integrating meditative practices into everyday life
Mindfulness in Plain English - Venerable Henepola Gunaratana
Going to Pieces Without Falling Apart - Mark Epstein
Path of the Heart - Jack Kornfield
Wherever You Go, There You Are - Jon Kabat Zinn
Journey of Awakening - Ram Dass