Norman Gevitz gives an in-depth brief history of Osteopathic Medicine in the U.S. in this book. It is a history of the struggles of osteopathic medicine -- struggles to grow, struggles to become known, and struggles to remain distinct from their MD counterparts. He touches upon it's inception and the background of how and why it came about. He then goes into a lot of history in chronological order of the growth of the DO schools and different programs, the politics between DO's and MD's and the government, and it's current and future state. He briskly mentions the key tenets of osteopathic medicine, but through the confrontation with the MD's organization, the AMA, we could understand where the DO's are different from MD's, or the lack thereof.
It's quite detailed, so be prepared. However, it is a very good history lesson for the lesser known side of the U.S. healthcare system.