Being a local or an outsider, a resident or a tourist can be just a matter of attitude. Sometimes I do consider myself a constant tourist, or a voyager, and always feel the need to explore the “foreign concessions” across Berlin, even Mauerpark, and the disappeared border between Prenzlauer Berg and Wedding, East and West.
So is Mauerpark also a border between two definitions of a flea market for “locals” or “tourists.” For old book lovers, I still recommend Mauerpark’s secondhand book stands. The fact that one has to ask for price instead of knowing it beforehand can make some feel uncomfortable – it feels somehow like being judged by one’s appearance. After all, it is a flea market, not a bookstore. So there you will have your chance to test your bargaining skills.
The most important thing is: one shall not give up any chance to find what might be otherwise hard to be found in normal bookstores. Personally, besides some German and Swiss fairy tale books, I have found a baby photo album from ’60s East Germany.