UAVS recommends the following books for those wanting to understand the history and development of unmanned aircraft systems:

Reg Austin's "Unmanned Aircraft Systems: UAVS Design, Development and Deployment: UAV Design, Development and Deployment (Aerospace Series (PEP))", Wiley-Blackwell, 16 April 2010, 372 pages, hardcover.

Michael Draper's "Sitting Ducks & Peeping Toms: Targets, Drones and UAVs in British Military Service Since 1917", Air Britain Historians Ltd, 10 Oct 2011, 372 pages, hardcover. 

Both available through Amazon.  Click on the link required above.