If you have people in your life at work or at home who try to control you, then this is the book for you. It will teach you how to set boundaries for them. One must use caution, however, as a person can get carried away setting boundaries around themselves to the point of cutting themselves off from friends and loved ones and making their heart hard against true guilt that needs to be dealt with before God.
This would be something you would use for the person who asks you to babysit from 9-5 for $20 and they leave you with no communication for several hours beyond and don't pay anymore than the original amount. Then they call you up again a few days later at 10pm, getting you out of bed to ask you to babysit again the next day at 9am all day. When you say no, they whine that they can't find anyone else and ask you for phone numbers of your friends and/or ask you to call them at that late hour. One must learn to set boundaries with people like this. You can't allow them to guilt you into doing their bidding or you will be doing their bidding all the time.
Boundaries are for the proverbial in-laws who try to control your marriage through the use of guilt trips and creating conflict between you and your spouse.
There are many applications for boundaries but they must be used with care and not with abandon in every relationship because not every relationship is in need of boundaries since healthy relationships have natural boundaries.
This is a great book. Just use wisdom in applying it.