Books are wonderful - so what could be better than a book? A book about books, of course!After I saw John Dickson Carr: A Critical Study book mentioned both in Douglas Greene's biography of Carr and on Tangled Yarns, I felt I had to check it out.Douglas Greene described it as "filled with insights about Carr's writing and attitudes", and I have to say, it met my expectations! There are some great insights here, and it's extremely quotable. Only on one occasion did I…