What Christ Thinks of the Church: An Exposition of Revelation 1-3 by John Stott
Velvet Elvis by Rob Bell
A scripturally sound but nontraditional discussion of Christianity. Especially useful for yournger groups or for people who are skeptical of Christianity.
Space for God by Don Postema
An excellent small group book for groups interested in a poetic, visual and varied approach to spirituality. Each chapter contains biblical passages, as well as quotes from thinkers and artists such as Van Gogh, the Desert Fathers, and John Calvin. The chapters also include visual prompts (famous paintings, etc.), a reflection section, and exercises for groups or individuals.
Devotional Classics edited by Richard Foster and James Bryan Smith
An excellent source for those who want to read selections from historical Christian saints. Each chapter includes a brief bio about the person, an excerpt from the person's writing, questions for individuals and groups, and suggestions for further reading.

A Long Obedience in the Same Direction: Discipleship in an Instant Society by Eugene Peterson
A classic book that explores key principles of discipleship, including worship, service, joy, and (of course) obedience. The chapters are short, and there's also a companion journal book that may be very useful for small group discussion.

Streams of Living Water by Richard Foster
A great book for those who want a more challenging study. Divided into chapters on the various traditions of spirituality (contemplation, holiness, charismatic, social justice, evangelism, and incarnational living), each chapter begins with a timeline of important people and events in the history of that spiritual tradition. Following the timeline, the chapter then discusses, in turn, the life of a historical, a biblical, and a contemporary person who exemplify the tradition. The chapter closes with an in-depth definition of the tradition and a discussion of how to practice it.
The Emotionally Healthy Church by Peter Scazzero
The subtitle describes the book well: "A Strategy for Discipleship that Actually Changes Lives." This book looks at what is not working in the way we have done church and what we need to change in ourselves for good leadership, to be good disciples of Jesus, and for spiritual maturity. The book has a Discussion Guide for eight sessions on the six principles in the book. His follow-up book, Emotionally Healthy Spirituality (Integrity 2006) has a more individual focus and does not have group questions, but is excellent.

When People are Big and God is Small: Overcoming Peer Pressure,
Codependency, and the Fear of Man by Edward T. Welch
Great application of scripture and helpful tools to use to challenge the
struggles of living in our culture in a godly manner. Each chapter has a
"For Further Thought" portion for group discussion.

War of Words: Getting to the Heart of your Communication Struggles by Paul David Tripp
A helpful and challenging book for aligning our words with the hearts we desire to have. His suggestions and examples are practical and full of God's grace. Each chapter ends with a "Getting Personal" section for group study.

 

The Peacemaker: A Biblical Guide to Resolving Personal Conflict by Ken Sande
 An excellent guide for resolving conflicts by Biblical principles with grace rather than a hammer. Study and application questions at the end of each chapter.
The Dangerous Act of Worship by Mark Labberton
Discipleship Essentials by Greg Ogden
Simply Christian by NT Wright
Finding Common Ground by Tim Downs
  Becky Pippert...anything recent she wrote!

 

 Nooma videos - Thought-provoking and fresh spiritual insight from Rob Bell, pastor of the Mars Hill church. The videos come with questions for groups. Especially good for younger groups or groups with people who are new to Christianity.