This is the best book on this subject I have ever read. Elisabeth Elliot has the gift of wisdom and is at the top of my list of people I admire most.
I have owned several copies of this book all of which I have "loaned" out and which have not been returned to me (praise the LORD, I pray they are ministering to all who read them). I also have purchased several of these books as gifts for young and old alike.
This book spans the ages and times.