Answer: Swiss binding!
This form of binding is where the text block is fully glued to the inside back cover of the hard case that holds your book, while the actual spine is left free and visible. (“Swiss binding” does not refer to how your pages are bound together, but rather to the way the text block – already-bound printed pages – is mounted inside the case.)
While you see this method most often used in combination with Smyth binding, you can also choose to perfect bind, saddle stitch or side sew the inside pages.
(PRO members, don’t forget to get in-depth information on all your binding options in your PRO Guide to Binding.)