If you can find them fairly cheap, these Lancaster Pamphlets are well worth it for half-narrative, half-analysis introductions to their topics.
This one covers four long-lived rulers Brandenburg-Prussia that brought the disparate place to the fore of Europe in a century's time, setting the table for their most famous scion, Frederick the Great. Shennan expertly describes the foreign and domestic policies of George William (30 Years War), Frederick William (The Great Elector), Frederick I (King in Prussia) or III (Elector of Brandenburg), and Frederick William I (father of Frederick the Great). Their policies are compared and contrasted, common threads gathered, etc., all in a compact discussion that's not too hard to follow and that goes well beyond Wikipedia.
The little volume also includes a detailed chronology, nice little map, a genealogy, and bibliography that doesn't seem too out of date considering the book was published in 1995.
