So I highly recommend this book, especially if you want to get a feel for the energy of the nine types. Introductory book approaches the Enneagram from a positive standpoint and looking toward transformation. Great questions in the front of each chapter to elicit your type. Unfortunately, it did not seem to accurately describe my type - Seven. Too positive - and that's already a problem for we Sevens.
Some people love it.
Excellent book on working through type. I recommend it as a second book, after some familiarity with the Enneagram. Excellent book on the Enneagram - very meaty and academic. I loved it but would not recommend it as a first book. Also, is too dense for many people who are more interested in application of Enneagram to daily life.