Sticky pistons receiving a 1-tick pulse (essentially not retracting the block) causes the enchantment table to no longer register the bookshelves where the block above the piston were even though there is nothing but air between the bookshelves and the enchantment table. (2015-06-12_00.57.02.png, 2015-06-12_00.57.08.png)

Updating the air blocks between the enchantment table and the bookshelves seems to be the only way to "reset" the table, breaking the table and placing it back still causes it to not see the bookshelves. (2015-06-12_00.57.31.png, 2015-06-12_00.57.36.png)