The plus of Gerson's book is that Kelley went off the edge in his later years, probably due to stress overload. the last few chapters in his book he rants about the Sanhedrin Jew Medical Mafia. If you give him the Kelley book, then warn him about this upfront.
If you want to give him a short book that will give him a good primer on nutritional therapy, give him "The Cancer Battle Plan". THis book was written by a cancer survivor. It is not complete as far as a protocol, but for a person with cancer who is scared and unsure what to do, it is an excellent first step into the world of alternative medicine. I know, two years ago, I was diagnosed with serious colon cancer. This book changed my life.