Your friend saw this resource on bethinking.org and thought you should see it:
The Thomas Factor: Using Your Doubts to Draw Closer to God
Professor Gary R. Habermas wrote this book for 'Christians who doubt' as well as those who are just a little unsure about their faith.
See the full resource online by visiting bethinking.org:
is a collection of resources which aims to make sense of the big questions of life about God, Jesus and Christianity.