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.
I basically started dating at 26. Download some dating apps. Tinder, Coffee Meets Bagel, Bumble, ... Use them, meet some people. Ask lots of questions. See what happens. It's easier than you think!