Tell me about hanging out in bookstore cafes.

What are the modicums of etiquette when hanging about in a bookstore cafe such as Barnes and Nobles? Can one bring their own books, laptops, etc...? Is one expected to have purchased something if they are sitting around in the cafe? How long is it acceptable to hang around? These kinds of things. Details appreciated.

Pretend you are writing this to explain to an alien who is new to human culture. (Not addressed TO an alien mind you, but so that an Alien would understand provided they had a basic understanding of english vocab/grammer.):)

Dear alien: Based on your avatar pic, it looks like your people have evolved yoga ball asses to sit on comfortably. I am envious.

Anyway, it's usually pretty chill, but do remember that it's a business. I don't hang out too much at bookstores these days, but in most coffee shops (especially the ones that aren't chains like Starbucks), if you buy a drink, you can pretty much stay as long as you want. You can bring your laptop, and many of them offer free wifi.