What John does is the old psychic surgery scam, palming bits of blood and animal flesh to appear to be taking evil or infected flesh from inside some sick. He also uses an old carnival scam, where you insert a nail up the nose. Only he uses forceps.
Just like with any faith healing any cures are likely placebo effect. There are lots of reports of failures to cure people, dozens of lawsuit, and of women being molested and abused.
As far as John of God the man, there are hundreds of stories of inappropriate (any beyond) sexual contact with young attractive women in both Brazil and other countries. One that was extremely profound was of an American women who was asked by the `entity' to see John of God after he was finished seeing people for that session. While in his room she was sexually assaulted (according to her) and then an instrument was shoved up her nose. When she returned to the states, she immediately fell ill and was in the hospital for several days. I have no firsthand knowledge of her account but stories such as this are numerous and their are messgae boards on the internet with first-hands accounts of sexual misconduct.
A friend of mine went to the Casa while I was there for her asthma. A few minutes after entering `current' she started to have breathing problems. The next day she was brought to the local hospital. She passed away several days later. You could chalk this up to coincidence but I doubt it. I can clearly remember one of our last conversations when she was scolding herself for not having `faith' which the Casa subtly but effectively pressures people to have and limits ones ability to evaluate situations clearly.
There have been numerous other incidents of people ending up in insane asylums after visiting, becoming worse physically and so on. I would say these incidents are in the minority but would you ever go to a doctor whose negligence had resulted in the deaths of some of his patients - of course not hopefully. Plus, no one knows what really goes on there when people feel and experience weird things in their bodies that they have never had before. They just take for granted that it is loving and benign. `John of God' never broaches any of these topics.
I have no doubt there are many more stories/incidents like the ones I have mentioned but `John of God' never touches on any of these. Furthermore, there have been dozens of lawsuits filed against the Casa in Brazil with claims of negligence such as I have mentioned but interestingly and unsurprisingly none have ever resulted in a judgment from what I know.
As for myself, all kinds of horrible things happened to me since first going to see John of God that never had happened before and I wasn't some `new-agey' guy who was interested in such phenomenon. I was threatened and attacked physically and mentally after returning from the Casa in ways that would defy most people's understanding as well having been in near constant fear over my safety and life.
Could you go see John of God in Brazil and be healed and have a wonderful experience? Yes, it is very possible and many people who go there have one or the other. Healings do take place there and many people have gotten better from whatever was ailing them.
However, at the end of the day there are tremendous risks as none of us know what truly goes on there. Again, `John of God' only provides the alluring mythology of the man and the Casa pr talking points. Whatever goes on with John of God is not from this earth and this books fails to address in any way the negative stories and aspects of the man and the Casa where he works. `John of God' has no warning label.