When recipes from a book are indexed, they're assigned numbers that allow them to be displayed in the same order as the recipes appear in the book. That's the default display order when looking at a given book's recipes via the Book view -- whether on one's own Bookshelf or in the EYB Library -- and other sort choices are available.
However, if you look at the same book's recipes in the Recipes view, by clicking on "Search this book for Recipes", the recipes appear in a different (unspecified) order, and 'Book Order' is not one of the available sort order choices. It should be. In fact, it should be the default display order, as it is in Book view.
A member has previously asked about the discrepancies between the available choices for sort order between the Book view and Recipes view, I think, but I couldn't find the thread. Certainly, the two drop-down sort menus could be made more consistent: give a Z-to-A option for sorting recipes in Recipes view, and re-order the choices in the Recipes view dropdown to match more closely those in Book view: Book Order, A-Z, Z-A, Rating, Buzz, then Recently Added [which for recipes within a specific book is usually the exact reverse of Book Order], Author, and Date Published.