A couple of thoughts to use-
1. Multiple FOLDERS can be selected in the Folder panel by holding CTRL as you click each folder. All the images from the selected folders will be visible.
2. Always useful to create standard Collection of the images you intend to include in the book as the first step.
3. Always- ASAP, when you open the book module with your images- Click on the "Create Saved Book" button (it will only appear until 'saved')
4. In future always re-open the book for editing by clicking on the white arrow at the end of the Book Collection name in the Collections Panel.
5. You can add more images to the book by simply dragging the thumbnails from the Library Grid onto the saved Book Collection.
6. Newly added images will appear on the end of the Filmstrip.
The saved "Book Collection" is like a 'Smart Collection', it always automatically updates with every edit or alteration you make to your book design.
A saved "Book Collection" can also be copied by a mouse right-click to "Duplicate Book" and give a new name. This allows you to have different versions of a master book design acting like a template- Using another set of images is possible in the 'duplicate'.
Many thanks for this.
Maybe I am not using the correct folder panel but when I click the folder I wish to add while holding Ctrl that folder simply replaces what I already have open rather than adding the photos to my existing visible photo folder. Maybe I am not using the correct folder panel
Thanks for your help anyway.
Sent from my iPad
Now I am not sure of your OP question-
Where is the "Additional folder of photos" you speak of?
Do all the additional photos for your book exist in the LR Catalog Library?
Have they been imported into Lightroom?
Have you created a "Saved Book" collection after starting your book in the 'Book' module?
If you have a saved book, back in Library Grid view, just drag extra added PHOTOS from any folder, onto the 'Book' in the COLLECTIONS panel.
It is that easy.!