Admittedly, I flipped through most of this, because we're still doing okay. It just seems like common sense to me (catch up with what's going on with each other, be affectionate, don't be critical, learn to compromise), but I think of the toxic relationships I know, and I can see how what I think of as "silly exercises" can really help. Especially the last few chapters of the book, which give examples of frequent points of contention between couples, and show the difference between problems that are solvable, and those that are permanent, and focus on the former, to save yourself a lot of grief.
I am making a mental note though to express more of an interest in my SO's life. So that's my homework.