I under stand that torches and other blocks prevent book shelves from registering for the enchantment table, but their is no blocks between that area, only above it. It shows the bookshelves effect, but does not increase levels.

1st image shows nothing above the empty space between the bookshelves and the table.

2nd image shows that it gives the level 30 enchant as expected.

3rd image shows glass above the space while nothing is blocking the space between.

4th image shows the enchanted levels given from the 3rd image.

Note that the iron bar above the enchantment table works perfectly fine and does not affect the enchanted levels.

-The more blocks over the empty space, the lower the levels get as if you were covering the empty space.

-This should work as the enchantment table should accept the effects from the bookshelves because nothing is blocking it.