We do want to add this feature and it is still on our to-do list but we have a couple of major projects in development right now which means it could be a while. What I have done for a couple of members who wanted to index their books without ISBN numbers is add just that one book so they can index request it. The most recent one that went up is Composer in the Kitchen. So email us at [email protected] if you want to index an entire book and I will add it for you. It would help if you could send the Title, Sub-title, Author, Publisher, Date of publication, Format and # of pages. This is why we cannot add more than occasional books without ISBN numbers as it is a lot of work to enter all this manually.
If you interested in just adding a few recipes from your books without ISBN numbers, then it doesn't matter that there is no ISBN. For Personal recipes there is no link to the book so you can enter all the recipe ingredients/categories then enter the book name and page number in Personal Notes.