Svarta Serien
These are paperback covers belonging to a Swedish publication series of crime books from the 60s called "Svarta serien" - "The Black Series". What they also have in common is that they are all illustrated by one of my absolute favorites - Per Åhlin. I and his other fans are lucky because in the 60s he was very active as a book cover illustrator. Thus it is not hard to come by his works in antiquarian bookshops or thrift stores.