7x5 inches (17.8cm x 12.7cm approx)
Known in France and Belgium as "Le Cercle Infernal", this is the original Marabout publication by Hans Reusch.
This is the paperback book that followed the release of the movie.
c220pp, with an excellent cover featuring Kirk Douglas, Bella Darvi, Mercedes, and Ferrari.
The text is, of course, in the French language.