An interesting examination of how different segments of the human race have interacted with each other and their environments over time. Professor Diamond appears passionate about the subject matter and it is understandable that he sometimes appears not to be completely objective.
The subject matter is so complex that most viewers will recognise familiar topics, although some may notice omissions, but in all fairness, there is not sufficient room in both the film and the book for a full explanation of each and phenomina mentioned (eg when the consequence of the difference between temperate and tropical climates is mentioned, there is no real need to mention that this is largely due to the earths rotational axis (currently) being inclined 23.4 degrees from the ecliptic plane.)
As mentioned above, and in other reviews, there is some (understandable?) lack of objectivity, but these reviews also demonstrate that the subject matter is thought-provoking, which is possibly one of the authors aims.
And in another 13,000 years, current evidence suggests:
The inclination of the rotational axis will be reduced to 22.5 degrees
The moon will be very slightly further away