Why Are Phoenix Branch Libraries So User-Unfriendly?

I am personally aggravated when I visit my branch library of the Phoenix public library system.

When you look at the aisles of books, you have no clue what kind of books are in the aisle because the signs attached to each aisle contain only numbers and periods.

Thus, I am forced to either ask a library employee for help or use the computer to query the catalogue etc.

I strongly believe that visiting an aisle in a library should be as easy or easier than visiting an aisle in your favorite grocery store.

If I am not mistaken, most public libraries in the U.S. are set up in a similar way.