Are there good English-language sources on the German submarine SM U-1?
Short answerYes. Technical histories by Eberhard Rössler and broader works on a century of German U-boats are useful starting points, with Gröner valuable for source detail.
NotesEberhard Rössler's technical history of German submarines and a broader history of a century of U-boats are useful starting points for SM U-1 and its successors. Erich Gröner is also a dependable compiler whose source material can remain valuable even when a reader disputes his conclusions. Documentation quality and agreement with an author's interpretation are separate questions. Together, these works provide a route from one early boat into the evolution of German submarine design.