I couldn't recommend Mars and Venus on a Date more highly. I know the sample size is ridiculously small, but 5 out of 5 people I've given this book to have gotten married within a year. (These were also people who were looking to find someone to marry)
It sounds like none of them were with their future spouses when you gave them the book. I may be cynical, but marrying after less than one to two years of dating doesn't seem like a good idea to me.
