I have always found Nolo guides to be particularly helpful in various areas of the law. I have about 5 Nolo guides on different topics. I was glad to obtain this one through the publisher.
This edition of The Legal Answer Book for Families is a good resource to have and a good first attempt to answer those questions. It answers some pretty common questions about marriage, divorce and custody (including information for same sex couples). It also provides rather important information for Estate Planning (just do it people, it will save your loved ones time, heartache and trouble).
As others have mentioned, the book is not extremely thorough in its discussion. Rather, it gives you brief information as to family formation and so on. The book is concerned with the family unit (not property issues or other legal issues people may have.
This is more of an informational and education resource than a place to look for answers. If you need an answer, check with your local courthouse. They have people there trained in provided you with the information you need.