According to CS Lewis the one unique thing about Christianity is 'grace', so perhaps there is nothing more important in living a Christ-like life than getting a really good firm grip on grace.
And Terry Virgo's God's Lavish Grace is one of the best books available on grace. If I can illustrate it this way, I think Philip Yancey's What's So Amazing about Grace? is the best book that illustrates grace, the stories demonstrate grace beautifully. Just a wonderful book.
Virgo's book on the other hand teaches you about grace, it equips you with a more thorough biblical grasp of grace in the life of a believer, the difference between grace and law, (the treatment of Romans 7 being first rate) and how to both give of ourselves fully without drifting back into a functional works based faith.
As a church we're going to spend the autumn looking at grace and this book provides a superb foundation. Highly recommended. Essential reading in fact.