The wide reach of the author (looking at not only European customs, but the differing customs of the many Americas tribes, of the Asia peoples, of the Africans. Not in depth on each, but a good book for a starting place on researching such a subject.
This is a collection of marriage customs from around the world. Books like this are entertaining, but I'm always worried that customs got wildly misinterpreted at the time of observation. I read once that in many cases when western explorers asked the name of a strange animal, the native inhabitant would say "there it goes" or something on that order and the westerner would dutifully write that the name of this new species was "there it goes."
This book is getting a bit dated now and I have wondered more than once reading it whether the writer has accurately analysed the customs he addresses. The real frustration, however, is that there is no way to check references as the book is written without vaguely citing more than a couple of historians/anthropologists. However, where I was able to check the sources myself, I found the writer surprisingly accurate and astute.