As someone who spent my time getting my social psych PhD on the study of marriage and romantic relationships, I would strongly recommend anyone who is planning on getting married read John Gottman's the Seven Principles for Making Marriage Work. The title is a little too self-helpy for my tastes, but Dr. Gottman is a highly respected relationships / divorce research who has 40 years of research and nearly 200 papers under his belt. Even just being aware of what The Four Horsemen can be massively helpful. The TL;DR of Gottman's research was that how often you fight doesn't nearly matter as much as how you fight and how you emotionally feel after a fight.
I am also a big fan of Dr. Finkel (another highly respected relationships researcher) and his book, The All-Or-Nothing Marriage. (See here for a short article summary). The TL;DR is:
>Americans today have elevated their expectations of marriage and can in fact achieve an unprecedentedly high level of marital quality — but only if they are able to invest a great deal of time and energy in their partnership. If they are not able to do so, their marriage will likely fall short of these new expectations. Indeed, it will fall further short of people’s expectations than at any time in the past. Marriage, then, has increasingly become an “all or nothing” proposition.
I recommend the book "Seven Principles Of Making Marriage Work" by John Gottman.
This book is useful for anybody in a relationship, married or not. I read the book within the first month of meeting my boyfriend. Now close to nine years later, I still strongly recommend this book. ;)