I'm reading "A Frozen Hell: The Russo-Finnish Winter War of 1939-40" by William R. Trotter. Trotter explains that there isn't that much out there in English because of the translation problems. Trotter himself seems to have backed into the subject while he was studying the Soviet military. Trotter's book is an interesting read. I've only read the first two chapters, the first explains why the Soviet Union picked a fight with Finland, and the second dealt with Mannerheim, who, oddly enough, did not learn Finnish until he was fifty, sometimes needed interpreters to give orders to his troops, and, when he retired, moved to Switzerland. There are a few scenarios involving the Winter War, but not many. I'm not aware of any scenarios involving the later fighting.
There are actually quite many books of Winter War in English compared to the Continuation War (as we Finns call the war 1941-44). You might call the latter a "forgotten battle" of the eastern front. The fighting was fiercest during the offensive period in 1941 and when the Soviets made their first summer offensive in 1944. The Finns managed to repulse it after losing Viipuri (Vyborg). Because it wasn't a full success for the Soviets, their histories generally ignore the repulsing part, and because Finland changed sides in September 1944, Germans ignored it too. After the war the main thing for the Finns was to have good relationship with the Soviets, so not that much was published about the Continuation War, especially not in any other language. So for example the battle of Tali-Ihantala June-July 1944, which in scale was bigger than the 2nd battle of El Alamein, is quite unknown outside Finnish borders.
Regarding Mannerheim, after the war he was the President of Finland for two years 1944-46, but retired for health reasons (and moved to Switzerland). His mother tongue was Swedish, which wasn't uncommon for Finnish political and military leaders back in those days.
The eternal privilege of those who never act themselves: to interrogate, be dissatisfied, find fault.
- A. Solzhenitsyn