I recently created a couple of books with a French Doors structure. This is a book with two spines and two covers that open in opposite directions (like two doors) and a single back cover. For both I used a coptic binding on the spines, but you could use a simple pamphlet stitch, an accordion structure or a sewn-on-tapes structure too.
The first book is a travel journal that is covered with a Maine maritime map. The closure was make with 2 circles of card stock attached eyelets and tied with waxed thread.
The second book using this French Doors structure has a handmade paper cover and wooden button closure.