Chiseled bookshelf doesn't drop without using the silk touch enchantment

this was intended, you need to use silk touch to harvest chiseled bookshelf

Chiselled bookshelves don't contain books by default. If you add books to the bookshelf, they will be dropped upon breaking it. (This is consistent with normal bookshelves, which only drop 3 books.)

As mentioned above, you need the Silk Touch enchantment to get the block back.

Despite this being very likely intended, it's always best to get Mojang's declaration.

This may be intended, but something made of wood not dropping anything when you use a diamond axe on it is not very intuitive