This book was converted from its physical edition to the digital format by a community of volunteers. You may find it for free on the web. Purchase of the Kindle edition includes wireless delivery.
The U.S. Department of War was the United States Cabinet department originally responsible for the operation and maintenance of the United States Army, also bearing responsibility for naval affairs until the establishment of the Navy Department in 1798, and for most land-based air forces until the creation of the Department of the Air Force on September 18, 1947.
It's a book of regulations and instructions, so it's dry as dust. It's still a useful read for anyone interested in the US Army in the period between the Spanish-American War and the Great War. The content shows the army in a period of transition from it's 19th Century mindset, but not yet fully invested in modernizing.