The book is extensively researched and there are many fascinating historical tidbits. A few of the themes reappear repeatedly, like the spread of malaria and yellow fever and the extensive African diaspora that occurred through the expansion of slavery. These help to tie the narrative into a more cohesive whole.
However, despite being impressed by the scope of the book, I found myself getting bogged down in its somewhat digressive style and the mounds of material. To emphasize his point, Mann bounces back and forth in time as he looks at different geographical locations and repeats his observations, or refers the reader back to other chapters. It started to seem that Mann found organizing the voluminous material without editing some of it out was too complex a task. While there is much to be learned from this work, I had a bit of trouble seeing the forest for the trees.