Hitler's Nordic Ally? Finland and the Total War 1939-1945, Claes Johansen. 
A wide ranging examination of Finland's two wars with the Soviet Union, the period leading up to the Winter War, the uneasy peace, and the aftermath of the wars, looking at the political debate within Finland, the fighting, and the wider impact of the war in the other Nordic countries. Especially interesting for the light it shines on the rather murky period between the two wars, where parts of the Finnish government entered into a de-facto alliance with Germany without the authority to do so, and on the varying Soviet aims.
[read full review]