I read the original Science of Discworld a while back now and was very impressed at both the story and the scientific commentary. The commentary itself took a very wide scope covering everything from the beginning of the Universe, to Cohen and Stewarts concept of 'extelligence'. This book takes a slightly different approach. It covers the bit the original left out, i.e. us! The breadth of commentary is still expansive, although there is a strange fascination with Narritvium (you have to be a Terry Pratchett fan!) and it delves into many topics concerning human evolution and development. Pratchett (as always) tells an interesting story and calls on some of the favourites to add extra depth to the narrative (Granny Weatherwax is mentioned), which holds the story together nicely. My only complaint would be that due to the constraints on material, the scientific narrative is perhaps laboured somewhat. It is still compelling and insightfull, but when every other chapter talks about 'extelligence' again, it is slightly irritating. Apart from that, it is an all round excellent book that perhaps only slightly pales compared to the earlier publication.