This book covers a surprisingly wide variety of subjects. It's unusual for a manual, since the entire thing is quotes from leaders of the church (LDS), although they're categorized rather well. That's one of the things that makes it interesting, though.
Anyway, it's useful and it has a lot of good things in it. Anyone could benefit for it, with just about any kind of relationship. It's good to read and good for reference, both. I was first introduced to this book when it first came out while I was taking an Institute class called Dating and Courtship, in Oregon—it's the manual for the class.
This was used for an on-line course through Brigham Young University Independent Study. The course I took was "LDS Marriage and Family". The course was good in helping study the Lord's standards on dating, courtship, marriage and family. I did not read everything within the manual, but what was assigned for the class. Despite the fact that I'm married with children, I took what principles I could in my current station in life, as a husband, father, student, and member of the Church of Jesus Christ of Latter-day Saints. I enjoyed the talks and materials within the textbook. The manual could probably use a few updates with talks, but what's in it is still relevant today.
I think this book would be good for anyone to read (even if you are already married). It addresses conflicts that may be found in marriage and Christlike ways to deal with them. It also talks a lot about dating and ways to choose an eternal companion. It is organized according to topic, alphabetically, so it is fun to find talks and quotes on the topic that you are interested in. Very good/helpful book! I liked it a lot.
It's a manual so I wouldn't say it's "fun" reading, but it does help you understand more about what you and your partner should be working at. It's also a little outdated and I think some things have changed. :)