"Old Polish Traditions" is a good place to start learning about Polish food and customs.
The book has good, short, sections devoted to Polish customs and traditions. And, it has good recipes for a number of Polish foods, especially finer food. This is not a long book and there are many, many, Polish food recipes. However, it is a good place to start learning.
Read through the book and its recipes. Start with something simple, such as a mushroom soup. However, many of these recipes can be difficult and/or time-consuming. For instance, Bigos is a hunters stew, usually started with saurkraut and two or more types of meat and is rarely ready to eat in less than three days. Some of the recipes can be daunting, such as stuffed roast pig. Some of the dishes take time, labor, and much practice to achieve really good results. Paczki (doughnuts) and Pierogi are among this class. Some of the Polish dishes are not simple. For instance, I can make a white borsht in less than two hours, but a proper and better tasting white borsht takes four hours of work, spread over three or four days.
So, for a while, stick to the easiest recipes. If you like some of those, perhaps you should buy a cookbook with more Polish recipes to continue building your skills. Then, come back and start working on some of the more difficult recipes.
Simple recipes include: Dry-Roasted Buckwheat, Barley soup (Krupnik), Roast Beef Roll with Mushrooms, red-beet salad with horseradish, and date mazurek.