I think if I were actually putting together a curriculum (and not worrying about copyright/access), I'd probably have a lot more chapters of books and articles/papers/webpages/videos than I would complete books. And I think you need to bring in discussions/projects in some manner in any case.
When teaching yourself you need multiple sources as a stand in for things being explained different ways by a teacher or through discussions.
A fair metric is about 3 books where you'd otherwise use 1 in class.