Yule and Christmas: their place in the Germanic year

From the preface: "This book treats of the problems connected with the Germanic year - the three-score-day tide of Yule, the Germanic adoption of the Roman calendar, and the introduction of the festival of Christ's Nativity into a part of the German year, which til then had apparently been without a festivity. It traces the revolution brought about by these events, in custom, belief, and legend up to the fourteenth century. By that time, the Author believes, most of the fundamental features which go towards the making of modern Christmas had already come to have their centre in the 25th day of December."

Written in 1899, this book by Alexander Tille is available in a digitized version at Google Books.  Though focusing largely on Germany, Tille also devotes two chapters to Scandinavian customs regarding Yule and the Midvinterblot.