I've been asked many times about what books to read and what books have been the most helpful in my spiritual journey. Here are some topics and books I would recommend you reading and/or studying (in no particular order):

THEOLOGY
Christian Theology (3rd Edition) by Millard Erickson (Textbook)
Gift Giver: The Holy Spirit for Today by Craig S. Keener
Letters From a Skeptic by Greg Boyd
Jesus & the Victory of God by N.T. Wright (Scholarly)
The Challenge of Jesus by N.T. Wright
Paul & the Faithfulness of God by N.T. Wright (Scholarly)
Gracious Christianity by Jacobsen & Swatsky
The Prophets by Abraham Joshua Heschel
Death and Resurrection of the Beloved Son by Jon D. Levenson (Scholarly)
Miracles by Craig S. Keener (Scholarly)
The Dome of Eden by Stephen H. Webb
Subversive Meals by Alan Streett
The Divine Conspiracy by Dallas Willard
The Lost World of Adam and Eve by John Walton

BIBLE TRANSLATIONS
ESV
NLT
Kingdom New Testament by N.T. Wright
NRSV
NIV

BIBLE COMMENTARIES
For Everyone Series by N.T. Wright
New Interpreters Bible Commentary Volume IX (Romans) by N.T. Wright
Acts: An Exegetical Commentary by Craig S. Keener
The Gospel of Matthew by Craig S. Keener
The Gospel of John by Craig S. Keener

CHRISTIAN NON-VIOLENCE 
A Living Alternative by Harader & Green
A Farewell to Mars by Brian Zahnd
A Faith Worth Fighting For by York & Barringer
Disarming Scripture by Derek Flood
A Testament of Hope: Essential Writings and Speeches of MLK Jr. by James Washington

PRAYER
Book of Common Prayer
Common Prayer by Shane Claiborne & Jonathan Wilson-Hartgrove
Seeing is Believing by Greg Boyd
Present Perfect by Greg Boyd
Prayer by Richard Foster
Becoming the Answer to Our Prayers by Claiborne & Hartgrove
 
CHRISTIAN LIVING
The End of Religion by Bruxy Cavey
Beauty Will Save the World by Brian Zahnd 
Water to Wine by Brian Zahnd
The Irresistable Revolution by Shane Claiborne
The Prophetic Imagination by Walter Brueggemann
Blue Like Jazz by Donald Miller
A Year of Biblical Womanhood by Rachel Held Evans
Searching For Sunday by Rachel Held Evans

SPIRITUAL WARFARE
Understanding Spiritual Warfare by Beilby & Eddy
The Invisible War by Donald Grey Barnhouse
God at War by Greg Boyd (Scholarly)
Satan and the Problem of Evil by Greg Boyd (Scholarly)

DISCIPLESHIP
Transforming Discipleship by Greg Ogden
Defeating Pharisaism by Gary Tyra

COMMUNITY
The Cost of Community by Jamie Arpin-Ricci
Awakening of Hope by Jonathan Wilson-Hartgrove
 
POLITICS & RELIGION
Myth of a Christian Nation by Greg Boyd
Jesus for President by Shane Claiborne & Chris Haw 

BOOKS ON THE BOOK OF REVELATION
Reading Revelation Responsibly by Michael J. Gorman
The Book of Revelation by Richard Bauckham
Revelation for Everyone by N.T. Wright
The Most Revealing Book of the Bible by Vernard Eller

BIOGRAPHY
St. Francis of Assisi: A New Biography by Augustine Thompson 
St. Francis of Assisi: A Biography by Omer Englebert
The Pastor by Eugene Peterson

MARRIAGE & FAMILY
The Meaning of Marriage by Timothy Keller
The 5 Love Languages by Gary Chapman
Boundaries by Henry Cloud and John Townsend
Boundaries for Kids by Henry Cloud and John Townsend
Raising Grateful Kids in an Entitled World by Kristen Welch


FICTION
The Lord of the Rings by J.RR. Tolkien
The Hobbit by J.R.R. Tolkien
The Chronicles of Narnia by C.S. Lewis
Brothers Karamazov by Fyodor Dostoevsky
Chasing Francis by Ian Morgan Cron
The Shack by WM Paul Young