Not just any book, but the real thing, if you know what I mean. Most of the modern literature out there is pulp. Where's the meat.Yes there are so many solid older works that I believe we have to read before even looking at the poor confusing selection of materials available that are written in your age. I have alot of great recommendations for your son:Power Through Prayer by E.M. Bounds -(this changed the life of Leonard Ravenhill when he was a teenager, in his words I didn't go through this book, this book went through me').Normal Christianity by Watchman Nee -This book really has shaped my christian life early on and its written in a very simple language for the common lay person.The Pursuit of God by A.W. Tozer -This book is abit harder to grasp but its small size and chapter lengths make it something someone can mediate and digest on/The memoirs of Murrey Mcheyne by Andrew Bonar -This book has sculpted and changed alot of my christian life, its a recounting of the life of Robert Murray Mcheyne from his diaries.Also I would recommend getting him alot of short biography books that are small and digestable on the lifes of: George Mueller, D.L. Moody, John Wesley, George Whitefield, George Fox, (theres a book by oswald J. Smith called "Men of God" I beleive and its on the lifes of 3 men... one is John Fletcher, thats a great book to get also.I hope that helps :smart: