I just found a way to import the paper book I am reading, it is not too laborious, but I am kinda amused by how I managed to make it work.
- take pictures of book pages with my phone, one chapter at a time
- select them in gallery in reverse order, share to google keep as one note.
- in the browser version of Google Keep use function ‘grab image text’
- delete images from the note
- export to google docs
- remove line breaks with a help from an add-on
- save as txt
- drop it to Lingq as a new lesson