Take out the racks and add shelves.

Books. Lots of books.

Beautiful cabinet.

If you don't want it to look like a gun cabinet, rather than risk damaging the cabinet, you could cover/hide the gun related parts:

You could cover over the indents in the bottom of the center part with glass doors that is intended for the rifle stocks with a shelving board -- oak, preferably; if not ... maybe painted black.

With two more pieces of shelving board and a piece of trim board connecting them, box in over the indents intended to hold the barrels of the rifles.

With another piece of shelving board supported by short trim boards attached to the side of the interior, you could add yet another shelf.

You now have what could be a china cabinet and/or a curio cabinet and/or a bookcase.

sell it? take out the middle portion, add shelving, paint the whole thing? do you have a lot of books? crafts?

The cabinet would be a great display case for trophies, provided your family has such things. I would suggest you put a solid shelf over the areas that have cut-outs for holding guns and then display your treasures on them. The cabinet is lovely, and I hope you will enjoy having another use for it.

Where is it located in the home?

Two words . . . Bourbon Cabinet. At least that's what I would do. Store/display your bourbon and glassware.