> Masks for the rescue.

You can be identified by your gait these days, and even facial recognition has been modified to work even in the presence of (medical) masks. More exotic forms of mask covering the whole face would just make you stand out even more.

> Which information?

They just need to know what time you were in the bookstore making your purchase. From there they can follow the security footage forward or backward until they have enough clues to piece together your identity. If you're a regular at physical bookstores in your area the odds of remaining anonymous in the face of a proper investigation range from slim to none.

It's all probably technically possible, but requires a lot of resources currently. I doubt that bookstores do that on scale, unless you are targeted by a state actor.