From what I have gathered, Prussia was the amalgamation of states in the area before they became unified as Germany. But what led to the states identifying as Prussia and later Germany?
Interested in the leaders, cultures, and a timeline of unification. A simple explanation with leads to primary or secondary sources would be fantastic as my fiancee and I would like to do some reading before our honeymoon!
German History 1770-1866 by James J. Sheehan (1989) is good. It treats Prussia in the context of the other German states.
Bismarck and the German Empire by Erich Eyck (1950) might be your best bet. It is based on a series lectures by Prof. Eyck given at Cambridge with added material from his three volume work, Bismarck. It's in paperback and it is not too much to say that the history of Prussia from 1815-72 is very much Bismarck's work.
They both have lots of source citations but the sources are almost always in German.
For Prussia, including a discussion of its continuities (and discontinuities) with Germany, Christopher Clark's Iron Kingdom is essential. It also delves deeply into what the Prussian identity meant to its people. Often, it didn't mean very much, with the flipside that Prussia must be counted as a decently tolerant and liberal state right up until Bismarck, at which point, as Erich Eych will tell you, the good old Prussia of piousness, civil service and tolerance went a bit mad.