I have just finished the book Guns, Germs, and Steel: The Fate of Human Societies by Jared Diamond, and following this statement is the mandatory review.
The reason Jared Diamond wrote Guns, Germs, and Steel was to furthermore educate and inform those interested in the fate of human societies. He did this by going in depth on periods of time in the beginnings of the human race when people were first discovering each other and learning how to live. It depends on whom one is to say if the book is needed. A world history teacher would find it more necessary than a student would.
The author had to consult many sources because he definitely was not born with the knowledge to write a book about human societies. It seems he relied on evidence from: Books, universities and their newspapers articles, museums, and personal experience, if not more. He used maps that were very easy to understand. There were also tables used to organize certain areas of information (For example, food production) that were also easily understandable. Two small sections consisting of around sixteen pictures each, were used. They allowed the reader to see the different kinds of people the author wrote about very clearly. The pictures did not follow the text they were mentioned in immediately. But, the pictures did have text under them explaining the picture. As for the tables and maps, they followed the text they were in, and did indeed help clarify the information. Anything extra like the tables, maps and pictures, made the book more understandable, and easier to follow.
I can honestly say that this book was not entertaining . I can not say if the author persuaded me or not. He did ask a lot of questions such as "Why did one part of Polynesia get modern technology before the other part?". Then, he followed that with a lot of information, and it was not like he was trying to "persuade" me or steer me in any particular direction.