I’ve read only up thru the 4th Edition , & no reference can I find to Intro- or Extrovert . Certainly Introverts can be just as content & productive as Extro’s . ‘Till I’ve had a look @ this 5th Ed , I’ll comment only on the previous reviewer’s concern — I’d expect from my readings & personal contacts w/ the author that he’d not have or write from this bias. Depending on a particular reader’s or group therapist’s interpretation [sensitivities to] of reading / teaching / practice of Yalom’s views on the Interpersonal approach to Group therapy , one might mis-understand the author’s intent . Integrating ,as Yalom suggests , the Interpersonal approach w/ whatever other approaches used by a particular Group Therapist would broaden ,
balance & strengthen using this seminal author’s Very useful “Bible” of Group Therapy .
I’ve relied heavily on his work for 40 + very satisfying years as a group therapist , integrating extensive aspects of  TA-Gestalt , CBT , Ericksonian Hypnosis , & Existential approaches . Whatever one’s primary theory of personality or of therapy , I don’t think it’s possible to be a competent group therapist w/o strong acquaintance w/ Yalom’s work .   yalom.com/tap/summary
drbobdick.com