Personally, I didn't find 'In Defence of Smoking' well written and lacking in some places where I had questions and I may buy 'Slow Burn,' since the length (600 pages) would indicate that it goes into much more detail about the topic.Don's book was based largely on the research that I did.
Both books (Don's and mine) are now somewhat out dated. During the time since I wrote mine, there have been thousands of experiments, trying to induce lung cancer in animals by exposing them to smoke. All have failed.
Also, just recently, a British jurist conducted a lengthy trial on the issue of whether smoking causes lung cancer and concluded that it didn't.