The first visible spread is also part of the binding.
In a casebound book, an endsheet assembly helps connect the text block to the cover case. Part of it is adhered to the inside board; another part turns with the book block. That structural role explains why artwork near the joint can disappear into a fold or hinge even though it sits well inside the nominal page edge.
The opening experience is therefore both mechanical and visual. A plain coloured sheet can give a calm pause between the cover and title page. A printed endpaper can introduce a location, chronology, cast, motif or brand language. Either choice works when the sheet remains suitable for folding, gluing and repeated opening.
Choose the endpaper after deciding what it must do.
A decorative map asks for legible detail across an area affected by the hinge. A solid brand colour asks for even coverage on the chosen stock. An unprinted textured sheet asks for a shade and surface that sit comfortably beside the first and last text pages. These are different production questions, so “printed endpapers” is not a complete specification.
Discuss whether the endsheet is self-ended from the text stock, made from a separate paper, printed on one side or both, and expected to match another colour in the book. The final choice also needs to suit the binding method and text-block weight. The hardcover book printing overview places endpapers beside the other case, spine and cover decisions.
Treat the joint as a physical zone, not a line on a screen.
Keep names, keys, small symbols and other irreplaceable information away from the hinge and board turn-in areas defined by the current template. Backgrounds can continue through those zones when the design requires it, but a critical label should not depend on an exact fold. A narrow frame around an endsheet can also exaggerate small differences in folding and attachment.
For a continuous illustration, make a full-size paper mock-up and fold it where the binder indicates. Open it naturally rather than forcing it flat. This simple check reveals whether a face, word or route line falls into the joint. Protect the inner reading area with the book gutter and margin checks, but do not reuse those layout measurements for endpaper construction.
Keep endpaper artwork separate from ordinary interior pagination.
Name the files so the front pastedown, front free endpaper, rear free endpaper and rear pastedown cannot be confused with page one or the final text page. If the front and back designs differ, show their orientation with a labelled flat plan. If the same pattern repeats, note whether it should align, mirror or simply continue without a fixed join.
Confirm colour and content from the correct proof. A PDF can settle spelling and placement; a printed and folded sample is more useful for stock shade, show-through, hinge loss and opening behaviour. Keep the approval tied to the final case dimensions, because changing page count, text paper or board construction may change the cover and spine geometry described in the cover and spine setup guide.