The four stars are for the great pictures of glaciers all over the world, especially those from Greenland. Moreover, the book comes in a luxuary format, hardback in a slipcase - makes a really nice present!
The text between the pictures is rather personal and emotional. The author mainly describes his own transition from a climate change sceptic to someone who is convinced of the effect of mankind on climate change. He connects this with pleas to mankind to reduce carbon emission - specially addressed to North Americans, who obviously have the largest carbon emission per caput. As I said, the text is rather emotional, with some interspersed scientific facts. That's okay, the topic deserves it - but the manner how he gets these emotions across, is probably more appealing to Americans than to Europeans. Lets put it this way: I share the interpretation of the facts and the vision, but not necessarily the missionary style of writing.
For those who want to see a movie of the largest glaciar calving event ever imaged (and other time-lapse imagery): The 'Extreme Ice Survey' Webpage has a lot.