I noticed this when I was trying to fit an enchantment table into my rather cramped base. If there are blocks directly above the 3x3 ring around the enchantment table, the bookshelves on the bottom row are blocked, even though they do not appear as though they should be blocked, and they continue to emit particles.
Linked issues
is duplicated by 4
MC-13579
Any type of blocks 1 high over space between enchantment table and bookshelves remove bookshelf effect
Resolved
MC-81304
Bookshelves upgrading enchantment table because of pistons / stairs
Resolved
MC-104998
Enchanting Table detecting Bookshelf wrongly
Resolved
MC-136268
Bookshelves don't count for Enchanting Table
Resolved
Attachments
Comments 4
Probably Works As Intended. It's the floating book that receives the glyphs that fly from the bookshelves, rather than the table itself. If either the table or the book is blocked, then bookshelves on that side can't enhance the table.
Confirmed.