Yeah I agree, it is a very interesting zone. Unfortunately, it’s not that well covered in English, and probably even German. There aren’t any Osprey books which really cover it. You will get a little more from the German and Polish language Wikis and maybe the Swedish ones on the various towns and individual Griffin Dukes.
I did not find that much about Pomerania myself, I largely relied on some general histories of medieval Germany like this one
… and histories of the Hanse especially Philippe Dollinger’s The German Hanse / Die Hanse
which is very unfortunately out of print and hard to find. Jan Dlugosz also mentions the Griffon Dukes periodically.
But I did find one really good source, for a bit later period (16th Century) by a guy who was the mayor of Stralsund and later, (after getting in political trouble there) Griefswald. He wrote a two part memoir which I used in part as the basis of a paper. Has a lot of crazy stuff in it, including a detailed scene of a fight between his brother and some robber knights, a Landsknecht getting attacked by a pet monkey, and other wild anecdotes.
Unfortunately, the second part of his memoir about his time in Griefswald, which he provocatively subtitled “des Teuffels Battstube” (“the Devil’s bathhouse”) seems to be lost.
An English translation of his memoir is available here:
I think there is also some stuff about the Griffin Dukes and about a controversial 15th Century mayor of Griefswald named Henry or Heinrich Rubenow. This wiki mentions the incident I cover in the Baltic book where Eric II of Pomerania got into a fight with Sastrow’s militia over an incursion into the municipal forests.
Here is the auto-translate on the German language Wiki on Rubenow
I would look for German language websites and maybe books about whatever specific towns you are interested in, and also another good strategy I find is to look for castles / castle ruins on Google Maps and read the local language wiki on them, they will often mention skirmishes and other incidents which took place there, quite often between the nobles and the towns.
This site seems to have detailed histories of all the lords and ladies of the house of Griffin, but in German
Hope that helps!