I finished the following:
Osprey Raid #18: The Zeppelin Base Raids: Germany 1914 - I'd never heard of these before, but they were the first attempts at bombing with airplanes. Curious read.
Osprey Campaign #233: Boudicca's Rebellion AD 60 - 61: The Britons Rise Up Against Rome - Many of the Roman era novels I've read make reference to this event, so the book filled in some details for me.
Osprey Fortress #87: Saracen Strongholds 1100 - 1500: The Central and Eastern Islamic Lands - Perhaps the least interesting of the three books, I didn't find it very useful, for the most part.