People find a book that works for them and recomend it to others, who find it useful and the cycle continues.
I don't think anyone anyone pointed to the book as a miracle cure, but merely what has worked for others and been passed on as such on this site.
Personally, I saw the title for the book "Apocolypse Delayed" and it burned a hole in the back of my mind until I found a way to get it an read it. It was instrumental in putting the final nail in the coffin of my faith in the Watchtower. I had no idea that Ray Franz had written a book and even when I heard about it I wasn't too excited.
Eventually I read it and honestly, while interesting, it wasn't the "a-ha" moment for me since I was already out. Good, interesting, but not reflective of my personal journey.
Same with Hassan I think. It's not groundbreaking in the field, but it has had a groundbreaking affect on many people here.
Nothing wrong with that.