J.C. Ryle’s book on Thoughts For Young Men should be essential reading for all men in their 20′s. In typical Ryle writing style, it’s encouraging and convicting.
http://www.charlesnolanpublishers.com/Thoughts.htm

How to Read a Book (!) by Adler and Van Doren
The Life of God in the Soul of Man by Henry Scougal (in his Complete Works, since it was so short). He died at age 28.
God is the Gospel by John Piper
God Isn’t in a Hurry and On Being a Servant of God, both by Warren W. Wiersbe
Anything by Tozer, esp. The Pursuit of God, and Knowledge of the Holy. (My most used of his books is “The Best of A.W. Tozer” which is 52 of his best chapters, as selected by Wiersbe).
For wetting the appetite to read, either Walking with the Giants (longer) or Victorious Christians You Should Know (short) by Wiersbe
Playing With Fire: How the Bible Ignites Changes in Your Soul by Walt Russell
Relationships: A Mess Worth Making by Timothy Lane and Paul David Tripp
One on the spiritual disciplines, either Donald Whitney’s or Hughes, The Disciples of a Godly Man/Woman.
With Christ in the School of Prayer by Andrew Murray
That’s my two cents. Thanks for asking.

Knowing God (J. I. Packer)
Desiring God (John Piper)
Recovering Biblical Manhood & Womanhood (John Piper, Wayne Grudem)
Living The Cross-Centered Life (C. J. Mahaney)
Reason for God (Tim Keller)
Crazy Love (Francis Chan)
Stop Dating Church (Joshua Harris)
and many more… but those are my recommendations. Hope this helps…

I’ll leave 10.
The Pursuit of God, Tozer; for passion
Truth Decay, Piercey; for worldview
The Mortification of Sin, Owen; for the obvious
Don’t Waste Your Life, Piper; so you won’t
Did I Kiss Marriage Goodbye?, McCulley; heart truth for the ladies
The Reason for God, Keller; to have an answer and learn to think
The Pleasures of God; to think and love bigger
Humility, Mahaney; to be humble
The Cross of Christ, Stott; to love the cross
Every Man’s Battle, Arterburn; to take lust seriously

5 that are well worth reading…
Knowing God (Packer)
A Call to Spiritual Reformation (Carson)
Suffering & the Sovereignty of God (Piper)
God’s Big Picture (Roberts)
The Discipline of Grace (Bridges)

Desiring God & When I Don’t Desire God by John Piper
Attributes of God by A.W. Tozer
Disciplines of the Holy Spirit by Gregg and Tan
Living the Cross-Centered Life by CJ Mahaney
Fool’s Gold: Discerning Truth in an Age of Error by MacArthur
Perspectives on the World Christian Movement (it’s class with a book) edited by Winter and Hawthorne
These are a few that come to mind…

Most of the ones I thought of have been mentioned, but another “must-read” is
Engaging God’s World by Cornelius Plantinga.

A Severe Mercy by Sheldon Vanauken

These were already mentioned, but I wanted to ‘second’ them:
Living the Cross-Centered Life by CJ Mahaney
God is the Gospel by John Piper
When I Don’t Desire God by John Piper

Lots of good ones listed. I’ll echo a few …
Knowing God – Packer
Desiring God – Piper
When I Don’t Desire God – Piper
Living the Cross-Centerd LIfe – Mahaney
The Cross of Christ – Stott
20 Basics Every Christian Should Know – Grudem
Stop Dating the Church – Harris
Total Church – Chester and Timmis
Humility – Mahaney
On a less “religious” side, read some good bios / adventure stories / novels…
Robinson Crusoe – Defoe (for you, Justin)
Some Dostoevsky
Ambrose has good history stuff – Undaunted Courage, WWII books

Proverbs
The Confessions – Augustine
The Godly Man’s Picture – Watson
The Weight of Glory – Lewis
Exegetical Fallacies – Carson
Religious Affections – Edwards
Always Ready – Bahnsen
Amusing Ourselves to Death – Postman
Anything by Flannery O’Connor

-Ecclesiastes
-Blue Like Jazz (Miller)
-Desiring God (Piper)
-Don’t Waste Your Life (Piper)
-This Beautiful Mess (McKinley)
-Knowledge of the Holy (Tozer)
-Radical Reformission (Driscoll)
-Pensees (Pascal)
-Practice of the Presence of God (Brother Lawrence)
-Mere Christianity (Lewis)
-The Reason for God (Keller)
-Happy Sleep Habits, Happy Child (Weissbluth)
-James, then Galatians, then James again
-Ecclesiastes (again)

Great lists so far.
These have been vital for me.
Ministries of Mercy – Tim Keller
The Hiding Place – Corrie ten Boom
A Hunger for God – John Piper
The Doctrines of Grace -Phillip Ryken
He is There and He is Not Silent -Francis Schaeffer
Real Sex – Lauren Winner
When People are Big and God is Small – Ed Welch
The Enduring Community – Newsom and Habing
The Picture of Dorian Gray – Oscar Wilde
Never Eat Alone – Keith Ferrazzi

Living the Cross Centered Life by CJ Mahaney
The Holiness of God by RC Sproul
Dont Waste Your Life by John Piper
Lectures to My Students by CH Spurgeon
Mere Christianity by CS Lewis
Orthodoxy by GK Chesterton

I’m assuming “the Bible” is going without saying. At 31 I’ve ended my 20s relatively recently, and these are ones I’m glad I didn’t miss.
God’s Big Picture – Vaughan Roberts (or the Moore College overview of the Bible)
Know and Tell the Gospel – John Chapman
Dig Deeper – Beynon & Sach
The Screwtape letters – C.S. Lewis
Disciplines of a Godly Man/Woman – Hughes
Knowing God – Packer
Thank God It’s Monday – Green
Too Busy Not To Pray

The Gutter
Blue Like Jazz
Velvet Elvis
Beautiful Mess-Rick McKinley
Faith-Charles Colson
Irrestible Revolution-Shane Claiborne

War & Peace – Tolstoy (it’s like Jane Austen meets Tom Clancy)
When I Don’t Desire God – Piper
Don’t Waste Your Life – Piper
The Holiness of God – Sproul
Mere Christianity – Lewis
Lord of the Rings & The Hobbit – Tolkien

The True Christians Love to the Unseen Christ by Thomas Vincent

Pilgrim’s Progress, Bunyan

Being in my mid-twenties, these are the books that have had the biggest infulence on my life.
Did I Kiss Marriage Goodbye? – Carolyn McCulley
Living by the Book – Howard Hendricks (An awesome, user friendly book on how to study the bible)
When I don’t Desire God – John Piper
All of Grace – Spurgeon
Passion and Purity – Elizabet Elliot (Although very cliche, there is a reason this book is a classic)

Attributes of God- A.W. Pink. I’ve been through 4 copies since I turned 30.

The Imitation of Christ / a Kempis
unChristian / Kinnaman
The Divine Conspiracy / Willard
The Normal Christian Life / Nee
Christ Plays in 10,000 Places / Peterson
The Reason for God / Keller
The God Who is There / Schaeffer

Oh yeah, add to my first list, above:
Knowing God by J. I. Packer
Don’t Waste Your Life, Battling Unbelief, and When I Don’t Desire God by John Piper (he is a tremendous gift to the church, as are others)
Humility by C.J. Mahaney (or better yet, the same title by Andrew Murray)
The Pursuit of Grace (and Holiness), both by Jerry Bridges
Hopefully my wife will chime in with a godly woman’s perspective.

I agree with a lot of the ones mentioned, and I would add ‘The Silence of Adam’ by Larry Crabb to the list.

The Divine Conspiracy (Dallas Willard)
A Community of Atonement (Scot McKnight)
Man is Not Alone (Abraham Joshua Heschel)
unchristian (Kinnaman, Lyons)
From the lists given above I think these books would all be worth a look and a good addition to give your group some perspective outside of “the tradition”. I like reading some of Piper and Driscoll, but I have really enjoyed these in the past year.

I have 3-ish must reads that come to mind:
Desiring God, and The Pleasures of God (Piper)… these so majorly impacted my understanding of the sovereignty of God.
God’s Design for Women: Biblical Womanhood for Today (Sharon James)- the best and most comprehensive book on biblical womanhood I have ever read. Also a great historic run-down of the various feminist movements in the world, and the “bennies” v. drawbacks. My book’s pages are tattered! HIGHLY RECOMMENDED!
http://www.amazon.com/Gods-Design-Women-Biblical-Womanhood/dp/0852345038/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1222227366&sr=8-1

I’m seeing a lot of good things on this list. I always suggest reading a good survey of church history, since knowing our history is so important to understanding who we are. I recommend any of the following:
- Justo L. Gonzalez, “The Story of Christianity”, 2 vols.
- Everett Ferguson, “Church History” (1 vol. at present, hopefully a second coming soon)
- Bruce Shelley, “Church History in Plain Language”
I haven’t read the third personally, but I’ve heard good things about it. The first two are excellent.

Thanks for the comments everyone. This is helpful.

I love books and I am in my 20′s so here goes Justin, hope it helps
1. God’s Big Picture by Vaughan Roberts
2. Desiring God/ Pleasures of God by John Piper
3. The Quest for More/Instruments in the Hands of the Redeemer by Paul Tripp
4. Not Even a Hint by Josh Harris
5. Charity and It’s Fruits by Jonathan Edwards easy Edwards reading ;)
6. Biblical Manhood and Womanhood by Grudem/Piper
7. Radical Reformission by Mark Driscoll
8. Keep in Step with the Spirit by Packer
There’s many more out there

Pleasures of God – John Piper
Knowing God – J.I. Packer
The Call – Os Guiness
The Pursuit of God – A.W. Tozer
Mere Christianity – C.S. Lewis
The Chronicles of Narnia – C.S. Lewis
Heart for God – Sinclair Ferguson
The Christian Life – Sinclair Ferguson