He also provides details of choosing an appropriate therapist when needed. One that encourages people to just "get over" past challenges is not helpful. If there has been some harm or betrayal, this must be fully understood and worked through before getting "over it".
The physical relationship is also an important part of a good relationship. This is an area that is often rife with miscommunication. People have different goals and feelings regarding intimacy. It is important to bring these out in the open and not assume the partner feels the same.
A relationship will never be perfect. However, people need to continual work together to improve it. It would be interesting to strap on some of the monitors that he talks about to evaluate conversations in the process. Maybe we can apply scientific analysis to ourselves to better understand what we are feeling "in the moment". (Then again, watching our recorded "fights" may be especially cringe-worthy.)
This book is part narrative and part laundry list of actions based on Gottman's relationship research. Successful marriages don't avoid conflict. However, they know how to deal with it. Couples need to identify areas that are negotiable and those that are not. Spend time on the areas where benefit can be achieved. There are also key areas in which men and women often differ. These seem to be present throughout different cultures. Males tend to take a stronger role of authority. Women tend to value cleaning more and are more concerned about feelings. There are many other things that tend to be over-represented in one gender (though that they are applicable to all couples or individuals.)