The book was suggested to me by a CBT practitioner. It languished on my shelf for several years because it sat adjacent to a bit of new age fluff, and I thought the subtitle sounded like it was another bunch of lost-wisdom-of-the-ancients drivel. I thought wrong: one should not judge a book by its cover.
The book is serious -- Haidt is a social psychologist at NYU Stern School -- yet eminently readable. It pulls in relevant aspects of the "ancient wisdom," evaluates them in the context of contemporary research, and shows where they can help us today and where they are outright plain wrong.
I can't say it has changed my life yet, but it has helped settle the inchoate bits that I have taken from the Enchiridon, Meditations, etc., into a useful way of thinking about the world and my place in it.
Now on to William Braxton Irvine...