Harold Ambler's Don't Sell Your Coat is a general introduction to global warming from the perspective of a card-carrying liberal who has had his eyes opened to all the problems with the AGW hypothesis.
This is one for the non-technical friend who needs a primer, an antidote to the propaganda that still seems to be all-pervasive. It's written with a lovely lightness of touch which should make it accessible to just about anyone. It has also been rather beautifully put together, with some very nice photos to pep up the inevitable graphs.
Here (with permission) is a chapter so you can see what I mean.
Buy it here.