Lots of Finnish books on the winter war but here´s some in English: The Winter War: The Soviet Attack on Finland 1939-1940 by Eloise Engle, Lauri Paananen A Frozen Hell, The Russo-Finnish War of 1939-40. Hardcover, 283 pages, lots of maps and photos. Written by William R. Trotter. Published in 1992. This is a great book, very well written. Approaches the war not only from a overall view but from life 'down in the trenches'. The author also gives a detailed list of other books relating to the Winter War. http://hkkk.fi/~yrjola/war/refs/ http://home.interserv.com/~tazio/7dSuomu.htm http://home.earthlink.net/~hwsportsman/WhiteDeath.html The last book by a German on the 1941 Barbarossa and the 41-42 winter battles that I read was "Moscow Tram Stop" by Heinrich Haape and I thought it was very good. He was a doctor so especially the situation of the wounded is told in that book.
Kai got there before I did with 'Moscow Tram Stop' ! Tow other classics which give memorable accounts of combat in unbelievably cold conditions are 'Paul Carell's two Eastern Front books, 'Hitler's War On Russia' and 'Scorched Earth' .
A short note on patrolling under winter conditions (WW II Italy) is found at http://www.milhist.net/mto/patrol.html
BTW, the Germans were actually getting some teaching in winter war tactics as a while ago I read that at least since autumn 1941 there were several courses arranged for German officers in Finland lasting 1-2 months with some 100-200 men per course.Unfortunately don´t remember the book but haven´t seen myself this being mentioned much elsewhere earlier.... It seems there was one course in 1941, and then 2-3 every year until Sept 1944 when Finland got out of the war with the USSR. Not many men but still shows that somebody thought the lessons would be of use.