There is a book I got from the library by Alan Wakefield, the Curator of the Imperial War Museum in London, called Christmas in the Trenches. For those interested in Military History or the World War I era in particular, I would highly recommend reading this book.
The book basically breaks down with several first hand accounts of every Christmas of the first World War. It talks about morale, and what people were sending to help out the troops, etc. It is truly a fascinating work, and very accessible for people not all that familiar with the First War World. It focuses primarily on British troops starting with Haig's British Expeditionary Force, which makes sense since the author is by the curator of the Imperial War Museum. The book also touches on Gallipoli and the Eastern Front as well as some of the things going on in Africa.
It is a good Christmas time read for history buffs.