There are a lot of diet books that have big claims.
Personally, my feeling is that if you, or in this case your husband, can stick closely to the diet it's likely to make inroads into better health.
The book that turned things round for me, personally, was Dr Bernstein's book. I don't follow it to the letter but my results have improved greatly in the 2 to 3 years since I read and took on the advice.
I think there are a lot of useful books which say largely similar things in different ways. My way of looking at it is if you can commit 80-90% (or so) to what the books ask, your health is likely to improve quite nicely.