'Redeeming Love' by Francine Rivers is one of the best Christian books that are fictional available in the market. Other great books are 'Winter's End' by Rebeke Lyn, 'The Barista' by Elijah G. Clark and 'Saving Grace' by Lesley Ann McDaniel.
Yea I have to second the shack! By far the best book I have ever read hands down! Never have I cried so much In a book or went wow! A friend recommended it to me and I found it in our library. Another good one is 90 min in heaven.