When you surround the enchantment table with 16 bookshelves, it is supposed to get the max tier of enchantments, that being level 30 as the third enchantment. However, now it does not do that, it only makes it to level 18. Disclaimer: I do not know if this was an intentional change but I looked back through the patch notes and that change did not appear anywhere in the pre releases. and I know I had a max enchantment table when I played in PreRelease 7.