mostly a waste of time, this book is too vague to be of any use. i don't care how the stats compare internationally, and i don't believe anecdotal stuff has any real value. give me the straight dope - i'm capable of analyzing it myself.
the biggest strength of their study is also their weakest: is it so wide (international, as i've mentioned) but including results from china or india - where cultural norms and/or economics are so different from here - can easily skew results. plus the 'findings' are based on internet questionnaires - that's what people will admit to, not necessary actually BE.
lastly, for a book that purports to have data on so many relationship parameters, they still wrote this sentence: It is worth considering that a very large number of men who visit prostitutes are married... with no data to back-up this claim (besides, who really cares? the data you could - and should - report is the % of married men who have used a prostitute, not a breakdown of said prostitute's client breakdown)

Turns out, couples who still hold hands after 9 years are the most happy.
Quick read- single people can skim some chapters.