There are a lot of things we do in life and in the pursuit of pussy that are not always legal. It is good that you are curious about the legality of the situation so that you are not flying into it blind and can do some proper risk assessment. Whether you are in Texas or some other state, there are some places where such activity regularly happens in bookstores despite the legal risks. There are risks. Just because a bookstore or private club hasn't been "raided" lately or yet, doesn't mean it can't happen that particular day you decide to play. Chances are it won't happen, but it could.
I believe part of the thrill of the bookstore play is that the people are playing in a semi public place. You don't know who might walk in or what other people may say or do while you are trying to have fun. For some that adds to the excitement and passion of things.
So you and the friend just got to decide whether you two are comfortable with the risks involved in such activity.