pb?Paperback. Typically 7" by 4.25" (18 cm by 11 cm) or smaller, though trimming errors can cause them to sometimes be slightly (less than 1/4 extra inch) taller or wider/deeper.
"Illustration de Maria Carella" on the back cover, and secondary French sources (NooSFere and others) credit the cover to Maria Carella. This is an apparent mistaken attribution based on the original Bantam edition's book design credit. That same Bantam edition clearly attributes the cover illustration to Jacobus.