The /data command can modify a lectern's Book NBT tag, but since it doesn't update the has_book block state, using the command to give a book to an empty lectern doesn't work–the lectern's state remains unchanged, so even though the necessary NBT data is present, the book is not rendered and right-clicking the lectern does nothing.

The same applies when using /data to remove the lectern's Book NBT tag. The lectern still displays a book, and right-clicking the lectern causes the book GUI to flash briefly before exiting.