For beginners:

• A Path With Heart: A Guide through the Perils and Promises of Spiritual Life by Jack Kornfield
• Beginning to See by Sujata
       Read this book online

For intermediate:

• Subtle Wisdom: Understanding Suffering, Cultivating Compassion through Ch'an Buddhism by Sheng-yen

For advanced:

• The Compass of Zen by Seung Sahn

For children:

• Dharma Family Treasures: Sharing Mindfulness with Children edited by Sandy Eastoak
• Wide Awake: A Buddhist Guide for Teens by Diana Winston

Integration of Yoga and Buddhism:

• Mindfulness Yoga: The Awakened Union of Breath, Body, and Mind by Frank Jude Boccio

Integration of Psychology, Science and Spirituality:

• all books by Ken Wilber website

eBooks:

• Awaken to the Buddha Within by Ven. Shi Wuling
       Get the eBook online (pdf)

For beginners:

• The Miracle of Mindfulness
• Peace Is Every Step
• Thich Nhat Hanh: Essential Teachings
• Living Buddha, Living Christ

For intermediate:

• Interbeing
• The Heart of the Buddha's Teachings
• The Sun, My Heart
• Going Home: Jesus and Buddha as Brothers

For advanced:

• Zen Keys
• Finding Our True Home
• Opening the Heart of the Cosmos
• Transformation at the Base

For children:

• A Pebble for Your Pocket
• Each Breath a Smile
• The Coconut Monk
• The Hermit and the Well
• Under the Rose Apple Tree

Novel:

• Old Path, White Clouds
  (a beautiful story of Buddha's life)

Poetry:

• Call Me By My True Names