We cycled it down from the Barent's Sea until we fell out with it somewhere in southern Finland. Some of the Finnish gravel roads were getting to me. They are completely ungraded and follow the contours litterally and the drops and climbs were so short and steep that you only ever spent your time cycling up hill with about 5 seconds off for a downhill before the next steep uphill...
When the author did the route, he rode it south to north (we met his son & some friends cycling it) and the book was then written North to South. A lot of the directions did not work and there was no signage when we did the Finnish section 3 years ago. I have to confess that some of those straight undulating roads were 'interesting'...
Some of the more interesting ones in the far north of Finland, on the Iron Curtain Trail.
The museum at the Winter War Memorial was very definitely worth going to btw. Each stone/rock represents a soldier who died there.