When I talk to Christian missionaries or people heavily invested in Christian mission, they almost invariably say that the book on mission is John Piper's "Let the Nations Be Glad." I've read "Let the Nations," and I understand why it's so highly thought of. It's also a long book, and deep.
I would describe "Live Life on Purpose" as Piper lite. It isn't watered down in the least, but it is considerably shorter and written in a way that, to me, is more accessible. Also for me, reading it has motivated me and encouraged me and possibly even changed my life (we'll see) in a way that Piper's book didn't. This may have had something to do with timing.
I would recommend it especially strongly for Jesus followers who find they are developing a heart for missions, but it's a little unfocused. This book will give you that focus. Warning: If you invite me to your high school or college graduation open house, you are likely to receive a a copy of "Live Life on Purpose."
A few excerpts:
The decline of the influence of the church in America is not because the world has become more secular, but because the church has.
Do you know what the Lord is searching the Earth for right now? It's a normal person who will allow the gospel to interrupt normal people life and normal people plans.
There are something like 600 churches and 460,000 Christians for every one unreached people group.
The gospel has the authority to interrupt our lives, moving us to a new position, sometimes toward risk and danger, in order that the gospel might be passed on through us to the nations.
The world mocks Christianity because they see clearly what we refuse to acknowledge -- the beam of the American Dream in our eye as we claim to live for the eternal.
"Lord, let me make a difference for you that is that is utterly disproportionate to who I am." (a John Piper quote)
The greatest danger is not that you will mess it up or fail, but that you will do nothing.