I’m glad I caved into curiosity and bought it.
In my opinion there is a strong parallel between the books of Barnes and Davies and the Conan Doyle biographies of Russell Miller and Andrew Lycett. In the case of Lycett and Miller both authors were, on paper, covering exactly the same thing and both produced books with positive and negative aspects. I found that owning both ensured that all bases were covered. Each one compensated for the other’s deficiencies (such as they were).
The same can be said of the film books of Barnes and Davies. Both have their up and down-sides and both complement each other. I would advise that any Sherlockian film buff buys both rather than relying on one or the other. Davies’ book is not as current as Barnes’ but I personally find Davies’ more readable and less like the reference book that both undoubtedly are. Davies’ book also has the major advantage that he lists his entries chronologically rather than alphabetically which is the approach Barnes takes. In my opinion this is Barnes’ biggest mistake and this shows up most when you endeavour to look up a non-English adaptation. I have even found myself using Davies’ book as a means to locating an entry in that of Barnes’.
Barnes’ book presents the information in a uniform and accessible way but I also found it a little clinical (but perhaps that’s just me). It could be said that where Davies’ book is full of opinion Barnes’ tends to be more “just the facts ma’am”.