John Reed's most famous book is Ten Days that Shook the World (later filmed as the movie "Reds"), an account of the Russian Revolution of October 1917, written from his perspective as a journalist who was actually there, in St Petersburg. The War in Eastern Europe was written a couple of years earlier, based on his wanderings through the war-torn Balkans. It may have helped give him a better foundation to understand what was to happen shortly afterwards in Russia, a country that was also wracked by war and defeat.
I read this book by journalist John Reed mainly because of Robert Kaplan's copious references to it in his excellent book Balkan Ghosts, which was written about 75 years later. Since Reed's book is about the First World War, and Kaplan's is about the prelude to the Yugoslav Civil War of the 1990's, one conclusion might be that little had changed in the region over the previous three quarters of a century. There's a lot of truth in that. Ethnically, religiously, culturally and geographically fragmented, with a long history of violent clashes between competing empires and nations, the south-eastern region of Europe -- the Balkans -- is blood-soaked even by the bloody standards of that continent.
Reed's book is almost that of a curious traveler and not so much that of a journalist. He has a telling eye for detail, loves political gossip, has an adventurous spirit and tells a good story, but he's not much of one for deep analysis of what was actually going on. This is curious, since he was a communist, and you would have expected him to look for deep underlying social forces. Instead, he leans far too heavily on sweeping ethnic prejudices -- Romanians are charming but shifty, Serbians are brave and open, Bulgarians are life-loving and welcoming, Jews are sinister, Turks are lazy, Greeks are sly, and so forth. In this, he was undoubtedly a product of his class, his times and his own national culture, to say nothing of his own personality, but it does make his explanations of events both dated and untrustworthy.
That said, Reed has some superb accounts of World War I in that part of the world. It's hard to grasp the scale of destruction and suffering and profound impoverishment across a vast sweep of the region -- in Romania, Serbia, Bulgaria, Macedonia, Turkey ... -- unless you read a first-hand account like Reed's. He was a man with acute powers of observation and deep reserves of compassion, whatever his other limitations. Having just visited much of the region myself, I found it fascinating to read his descriptions of the war in cities I recently visited, such as Belgrade, Sofia and Istanbul. If you're interested in the Balkans and its history, you'll find this book a good read.