It's Just My Nature, written by Carol Tuttle, is a guide to knowing and living your true nature (along with your spouses, and everyone you associate with). This book helps you identify your primary personality traits, thought processes, body movement, natural gifts, and much much more.
I have always loved and have done many personality tests and quizzes (including the four color groups: red, yellow, blue, and white) just because it fascinates me, but I love this book the most because it goes so much deeper and further than just personality traits. It really can better help you understand how your or your spouse's mind process gets from A to B, and other things like what might motivate one person and how it differs from another type. My husband and I have found this information extremely helpful in our marriage, knowing each other better, and knowing that it's okay that the other doesn't move and accomplish things exactly like we think it should be done ourselves. We are so much more understanding of why certain situations would make us feel certain ways or react differently than the other, and we can "let things go" more easily.
So I would in a heart beat, recommend this book especially for marriages, but also for yourself, or any other relationship that you have with people. OH, and it's helpful with children also, even though it's not really tailored to children, as parents you'd probably be able to figure out their true natures too and have it help with parenting. I can't stress it enough, read the book, both my husband and I have seen so much valuable knowledge for our marriage from it! And if you want to borrow mine, I'd be happy to lend it to you!
Here is a link to purchase your own, It's Just My Nature