The Magic Mountain by Thomas Mann — Not about Stralsund but about the Baltic coast mentality and the slow, introspective rhythms of northern Germany. Mann grew up in Lübeck, another great Hanseatic city, and his sensibility captures something of the character of this whole coast.
Pommerania: A Forgotten Province by various historical accounts — The region of Pomerania (Pommern), of which Stralsund was the capital, was largely erased from the map after 1945 when it was divided between Germany and Poland and its German population expelled. Understanding this history — the loss of a world — makes the surviving old town feel more precious.
Gorch Fock by Johann Kinau (pen name Gorch Fock) — The novelist whose pen name was adopted by the famous sailing ship was from Hamburg but wrote about North German seafaring life. His stories capture the culture of the Hanseatic coast and the men who worked it.