For some, not for all
You have to choose among your friends for beneficiaries of this recommendation. Some people can't bear the thought of personality types, and some people eat them up like candy. I found the expostions in this book helpful, but my experience with the Enneagram would indicate that it has to be taken with a goodly amount of salt. It gets extremely complicated. Riso and Hudson steer clear of anything that might be construed as religious, banking rather on the transcendent elements of "essence" and self-realization.
The descriptions of the nine types can lead to practical undestanding if you keep your balance. What is interesting to me is the kind of path opened to inner work. I find it helpful on the one hand, and extremely controlling on the other. I am so tempted to sigh, "How masculine..."
Surely worth a look-in, and for some might just be life-changing.