The book has a very ambitious goal: it attempts to explain the course of human history (in broad outlines) during the past 13 000 years or so.
More specifically, the book aims to answer "Yali's question" (a question posed to the author by a prominent politician in New Guinea): why Europeans conquered native Americans and not the other way around? Or, why some peoples and some cultures developed "further" and more rapidly than some others?
The author gives a very clear-cut answer to this. It's NOT about inherent differences in human ability, but rather about what different environmental settings afforded. This is the "deep" answer -- argued into existence very carefully and convincingly, and backed up by a lot of scientific evidence. There may be some more superficial answers (e.g. with regard to technology, language, governance structures etc.), but these are only proximate causes, all going back to the "deep" answer.
Was it good?
The book is just superb. Not only is it insightful and credible, it is also highly informative and entertaining in a lighter sense. Put shortly, the book is delightful to read throughout.
Moreover, the author must be applauded for the breath and depth of his knowledge; the scope of expertise required for writing a book like this is immense.
The main take-away for me?
The book really highlights the fact that we human beings tend to focus on quite shallow (or proximate) explanations for phenomena, whereas in most cases there probably is a "grander", "deeper" mechanism (or a bundle of mechanisms) at work. At the same time, however, this is not very surprising, because evidently uncovering such "grand" mechanisms is no small feat.
Who should read the book?
I would recommend the book for anyone; both the message and the style should be very generally appealing.
The book on Amazon.com: Guns, Germs, and Steel