Your friend saw this resource on bethinking.org and thought you should see it:
Relativism: the loss of 'truth'
Two sample chapters from Relativism: Feet Firmly Planted in Mid-Air
by Greg Koukl and Francis J. Beckwith.
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.