I don't have any recommendations but you might find the late Hohenzollern family and Hindenburg a bit more interesting in depth before focusing on him personally. The
Prussian aristocrats/Junkers viewed the socialists/SPD as a real problem/threat.
All history is intertwined with respect to warring European statehoods/principalities, and the Prussians really go back to
Andrew expelling Teutonic knights from Austria Hungary.