Jacqueline Susann isn’t the only author for whom publisher Bantam Books used Montage. Several of the paperbacks with novels by Jerzy Kosiński (1933–1991) feature this heavyweight by Ed Benguiat, too.
In the 1971 One Line catalog by Photo-Lettering, Montage is shown in a section titled “Engravers”, in widths ranging from Triple Condensed to Expanded. While the style on the cover for Steps (shown above) appears to match the Extra Condensed, the one chosen for Being There (below) is wider, possibly the Extra Bold.
The designer who was responsible for the type and layout isn’t credited.