I have to admit I prefer books containing facts, rather than theories, because I am a good theorist, so I swiftly lose interest in authors who propose a lot of half-baked ideas. This Diamond guy is not a historian or even anthropologist, just a biologist with a very scattershot knowledge of human history. Nevertheless, a very smart person can make good theories from a small number of facts, if they are knowledgeable enough. The question is whether Diamond falls into that category.
Having read some of this guy's theories and essays, I find that his method is not particularly scientific. He makes no effort to find or explain counter examples, nor does he make any effort to be comprehensive--an especially important factor for sweeping theories like this. When somebody formulates global theories based on anecdotes, it is a virtual certainty that the theory is incorrect.
For example, the vikings succeeded despite coming from longitudinal areas with sparse agriculture and lots of climate variability. So did the Japanese. Also, I see no trend. During the course of civilization you have one group sweeping around and destroying, then another. It's not like there are repeated successes from certain particular places that would indicate a pattern. Sometimes you have areas that are complete failures in one milennium, succeeding greatly in the next, or vice versa.
The idea that draft animals and wheat made the Eastern Hemisphere succeed seems naive and simplistic to me. The Eastern Hemisphere is more than twice the size of the Western. That alone gives it a big advantage.
Diamond's focus on disease is understandable, given his training, but as far as civilization is concerned, disease is not a big factor. Disease tends to kill off the weak. If anything, my experience and knowledge suggests that disease epidemics make civilizations stronger, not weaker. You can see this in herd animals. Predators kill off the weak and the herd becomes smaller, but stronger. Nietzche wrote, "What does not kill me, makes me stronger." (Twilight of the Idols) There is an element of truth to that basic idea.
Diamond's book has enough detail and interesting ideas to fascinate the average American, but I do not consider it to be a significant contribution to a new understanding about civilization, and for historical experts I would consider the book to be entirely superfluous, especially because its method and use of evidence is poor by scientific standards. The advantages of the book are that it is entertaining and for a person without much knowledge of history it may be interesting and educational as a collection of small historical essays.
For a person who wants to understand the development of civilization I think there are many books that are far more systematic, information rich, and have higher quality theories. That would include Gibbon, the Durants, Toynbee and even Spengler. These four authors all have a knowledge of history that simply dwarfs Diamond and it shows in the quality of their work. You would be far better off reading their books than this book by Diamond.