Admittedly, I read this from a place of wanting to see more about ISTDP out in the world, particularly from the perspective of a client, as there is so little of it out there for the general public. This definitely skewed my read, as the stuff that was in there about ISTDP was quite minimal and general (I think there was only about 1 page worth of personal experience shared about ISTDP, which was very surface-level - probably insightful if you hadn't heard of ISTDP before, but insights I had already gained from watching videos on youtube, such as those by Patricia Coughlin).
I feel like the book in general could have been cut back a bit. The writing can be a bit wordy. That said, there are some insights that ring true throughout the book, and I did end up highlighting quite a few passages because of that. I'd recommend it if you are just generally wanting some ideas on how to tackle symptoms you may be experiencing with no clear origins, and don't mind sitting through narration to get those insights.
If you are specifically interested in ISTDP, or open to challenging your beliefs, The Lies We Tell Ourselves by Jon Fredrickson, while a bit clinically sterile, is a powerful read that helped me to gain a new perspective on some of my behaviours.