What is the best treatment for this firepplace?

I'd paint it all, including the paneling.

I’d either paint it or tile over it. A picture of the room would be so helpful regarding the paneling

Paint is the cheapest fix or cover in new stone. I had white brick almost identical and we resurfaced to this stone. It went right over the top of the old. Fireplace and bar were both covered in white brick.

I’d say to clean it first. Move away all of the tools, the screen, and all the little dodads around it. Is it painted white or white brick? Once you have a clean, blank slate to look at then you can decide.

I’ve seen people with MCM design just paint those little bumpouts a color to match room decor. Don’t get crazy with tzatchkis.

😉

PS-Don’t forget to clean the fireplace itself or hire a chimney sweep if it has been many years since it was done! Do this before cleaning the brick.

With several colors of paint, a dry-brush technique can give a lovely old-brick look. You can choose colors that compliment your decore, and change them as the decore changes.

To have the whole thing thoroughly cleaned was my first thought also...What color of furniture you are placing in this room? Old fashioned, wood? or you are trying a more modern/contemporary look?...What kind of floor you have?...are you adding a rug?....all that will give you an idea of what would be the way to go with the fireplace surrounds...Have you thought of a big mirror or a good size painting? Stick with bigger items but few … JMO

perhaps you could look on Pinterest or other websites such as Houzz or Apartment therapy at the pics of mid century modern homes for some ideas. Mid Century modern homes are quite highly valued nowadays and seem to increase in price quicker than other homes. So it might be wise to be careful about what you do so that you don't devalue your home.