This was Fr. Seraphim's best and most important book, in my opinion. And yes, it is also one of the most important and influential works I have ever read in my life. I've read it at least three times, and I keep getting something new out of it each time. I first read it when I was a catechumen some 15-16 years ago. That and Dr. Kalomiros' work Against False Union were the most formative books of my years as a new convert, and really helped me understand why ecumenism is a heresy and an evil which may very well usher in the last age of this world. Current world events reinforce this understanding every day.