I've got that window when trying to place any blueprint from books at any place (standalone blueprints still work):

Error while running event beltlayer::on_put_item (ID 9)
Item is not blueprint.
stack traceback:
beltlayer/lualib/BaseEditor/BaseEditor.lua:649: in function 'on_player_placing_blueprint'
beltlayer/lualib/BaseEditor/BaseEditor.lua:1110: in function 'on_put_item'
beltlayer/Editor.lua:463: in function 'on_put_item'
beltlayer/control.lua:44: in function <beltlayer/control.lua:44>
stack traceback:
[C]: in function 'get_blueprint_entities'
beltlayer/lualib/BaseEditor/BaseEditor.lua:649: in function 'on_player_placing_blueprint'
beltlayer/lualib/BaseEditor/BaseEditor.lua:1110: in function 'on_put_item'
beltlayer/Editor.lua:463: in function 'on_put_item'
beltlayer/control.lua:44: in function <beltlayer/control.lua:44>

Same, and no idea how we'd fix this manually.

Thanks for the report! Should be fixed in v0.6.4.