Interesting topic.
I agree with RebYidd that children should have a library card and go together to the library.
Supervision is also very important. With the sadly lowered morality of the world around us, it is important to make sure that our reading material does not affect us negatively in a spiritual way.
Personally, I prefer to place a hold online for books I want and then pick them up, because browsing exposes us to so much garbage.