I highly recommend this book, to myself(!) and to others.
In general I hold highly of the writings of Miriam Adahan- the reason for that I can't go into it fully here. But very basically; kind of like the book actually says- you can't serve G-d if you don't even know who you are. That's why we have to know a certain amount of psychology. But alone, psychology is very devoid of G-dly-ness. It's hard to know how it affects you in an 'ethical' way . And that's why a legitimate religious-Jewish approach towards psychology, which not only integrates the ideas of mussar into it, but is only used as a tool to fully understand mussar (especially in the 'innovative' way it was understood in Lithuania and beyond) is necessary. This is one of those books.
As for a description, uhh, well, this is what the Feldheim site says "An in-depth analysis of the nine principle personality types, based on an amazingly accurate, ancient classification system called the Enneagram. The author demonstrates how an understanding of one's strengths and weaknesses can lead to spiritual growth".
Want to buy it?(!)