This is my first book by the Swedish writing couple.
The book starts with a great opening: eight occupants of a bus are murdered. Among the dead is a colleague of police detective Martin Beck. The entire book is about how this crime is solved and for a long time there are no clues or motives. This is a pure police procedural with detectives working through masses of details until a link is found with a 16 year old unsolved murder case.
There were too many characters, both detectives and suspects or witnesses. This makes for realism but it was slow and rather boring reading as a result. The book does capture the atmosphere of the time and place, a 1968 Stockholm winter.