Getting the Love You Want by Harville Hendrix is a tried and true classic, and has been indispensable for me and Yotam. Hendrix explains how we are drawn to partners because the very ways they will most ask us to change are the places of growth we most need to do. This is called finding your imago. I highly recommend couples read this book through before marriage.
Nonviolent Communication by Marshall Rosenberg creates a framework for communicating by clearly expressing your emotions, values, needs, and requests. In our home it is used in almost every conversation, especially the hard ones. It is hard to learn NVC from a book - but you can use it as a reference, and there are good anecdotes. It’s kind of a whole philosophy of being human, and seeing other people as having the same basic needs as us.
Internal Family Systems, developed by Richard Schwartz, teaches that we are all made up of parts that long for the compassion and love of Self. Self is courageous, clear, compassionate, curious, confidant, and no matter what we’ve gone through in life, Self is always in us if we can access it. Our parts are like little personalities or characters that emerge as a response to life. They have their own feelings and beliefs, that are often outdated or not in our current best interest. The existence of parts explains why we usually feel multiple emotions at once, and why it can be hard to tell your partner exactly what you think about something important: you have different parts that think different things! Learning to differentiate from a part, hear what it has to say, and send it compassion is a life-changing practice. Learning that your partner is made up of parts, too, and allowing that… well, I personally think that is a foundational practice for a sustainable relationship.