A standard resource that I recommend (and give out) regularly is The Peacemaker by Ken Sande. It is filled with solid instruction for resolving conflicts in a biblical, God-glorifying manner. The truths here can be applied to marriages and any personal relationships.
Nancy Leigh DeMoss, Lies Women Believe: And the Truth that Sets Them Free (Moody) I recommend everything Nancy has in print; but this book and workbook has been especially helpful to women across the world in recognizing lies they’ve believed about God, priorities, marriage, emotions, and more. This resource sheds light on how we can be delivered from deception’s bondage and set free to walk in God’s grace, forgiveness, and abundant life.
Seeking Him: The Joy of Personal Revival (Moody), is a twelve-week workbook filled with lessons on crucial topics for spiritual growth. This convicting yet encouraging resource by Nancy Leigh DeMoss and Tim Grissom takes you on a journey that will deepen your relationship with God.