From an article in the Helsinki Times:
...the fifth book, Helsinki Dead, was set for release this year but its status is unknown. Thompson also contributed to Helsinki Noir, an anthology of short crime stories which is scheduled for publication this November.
From Terry's Euro Crime review of Snow Angels, the first book in the series:
SNOW ANGELS is an astonishing good first rate police procedural thriller. Extremely violent and so may not be for those that are particularly squeamish, but the author has the gift that the best writers have, which is to completely transport you to the world of his imagination all within a few pages. Finnish is a very hard language to learn and the names of characters in the story seem very strange to my eyes, but because of the writer's huge skill, this does not stop me enjoying this mesmerising story.