You have some very intelligent doubts about Carbon Farming. I took Eric's course in March in Vermont, and he was very diligent about discussing the limitations of all the various solutions presented. He discussed the limits of soil carbon sequestration, but also presented a variety of other interesting solutions. He critiqued the "miracle solution" discourse often associated with techniques like holistic grazing, amongst others.
In fact, Eric is so balanced and meticulous in his research that I am surprised by the name of his book - "The Carbon Farming Solution" sounds like another miracle-cure, but in fact, as you will probably see when you read through the book, he is not claiming at all that there is one single solution to all of the world's problems...
Anyway, I think a reading group is a great idea for this book. The course was amazing, and if you have met Eric, you should feel confident about the quality of his research and the fairness of his arguments.
Enjoy it! I will try to keep up!