NORA
I dont think there is any particular book dealing with world wide
Mytilus but if you try on library loan or through your local museum
library the old Reeve 1856 publication Monograph of the genus Mytilus
Conchologia iconica or illustrations of the Reeve shells of molluscous
animals. (Reeve: London). 9:pls 1-18. Describes and figures 61 species
world wide which would probably have the species you are seeking to ID
Kev