Two book covers from the Martin Beck series, collectively titled 'The Story of a Crime'. Both covers are almost opposites, one a watercolour, the other and photograph; Roseanna showing just the head, while The Man Who Went Up In Smoke shows a business suit in motion, sans body - it wafted away with the title.
The writing duo of Maj Sjöwall and Per Wahlöö each wrote alternate chapters for every book, a sort of collaboration I find particularly amazing - the ability to create characters, from the brains of two people, and keeping a believable continuity to their personalities.
I wonder if you can tell which chapters are written by whom? Did Maj Sjöwall take the odd numbers, and Per Wahlöö the even? Did they switch that around every book, so as not to give the game away? There is something pleasingly rounded and symmetrical about the whole process, in the way I find happiness in every Tintin book being 62 pages long.