First of all, can we have a little more info about what has already been done or what is intended? Do you want the bookcases to stay, have you already painted, are you open to changing art?
My first suggestion if keeping both sides of fireplace with existing shelf units would be to align the shelves the same on both units. Then get a larger piece of art which will take up almost the entire space above fireplace, even with tops of shelves or possibly taller. You can tape it out with painters tape to see how you would like either idea for art size. I like your art work just think it needs to be bigger.

cindy is right: fix this with paint

the bottom is one of my favorite houzz photos because it really makes the television part of the design.

You could paint the outside of the cabinets a new wall color and the inside darker so the tv visually disappears.

You can also put something on the far left like a long painting or tall plant to balance the area better.

The issue appears to me to be that in most cases like this, the mantle and fireplace are out to the edge of the build-ins or bookcases so they work as a unit. In your case,your mantle barely comes to the edge of them making them overpower the fireplace wall. This might be one of those times when something else belongs there as I don't think you're going to make those look the way you want them to because the fireplace is too shallow.

I agree with Hayley, the bookcases are not flush with the FP, it would be fine the other way around, but this looks really odd. Plus the fact that they are not balanced. Are these cabinets you just bought? Can you return them?

This does not bother me, as it seems the cases are from the same manufacturer, are they? and same paint color as mantel basically.

I have many photos in my books with a bit off from symmetrical.

Maybe paint area above fireplace a darker color as an accent and then put the TV over fireplace. I probably never said that before! But in this case it could make the TV disappear more and provide some balance. Please first rearrange those shelves and repost.

Are these actually "built-ins?" Wondering why one is more narrow.

lessismoore, no, they're a couple of bookcases the OP wants to use as if they were built-ins.

I would put a picture up that almost but not quite reaches out to the bookcases. Are the bookcases painted the same color as the mantle- hard to tell, if not they should be. The lack of symmetry is odd and mantle not extending is a problem, but let's tackle wall art and painting first.

I don't think you'll ever be happy with these unless you hire a carpenter and have him/her actually make these built-ins. Is this your only room for the TV? I would be tempted to mount the TV over the fire place and place two chairs or benches where the book cases are and hang some art work on those walls.

Off topic but I like how mat is white with 'light' art with paint. Nice to have a wood fp. Maybe you'll post a bit more of your room? Possibly another owner would place chair there - why build?

Would moving both bookcases away from fireplace help? Foregoing the built-in-look idea. (I realize there is not a lot of room).

In regards to my last post, switching the bookcases would give you extra room.

the wall color is throwing it off i think, the tiles in the fp are blending, and everything is just 'popping' the bookcases not to match. I would try removing the left one all together.

If we are going to move anything, I would remove the smaller left hand bookcase and put it somewhere else. Then move the right hand bookcase so it is centered on the small wall, pulling it away from the fireplace. You are never going to get a built in look from this. Then I would paint the bookcase the same color as the woodwork with the inside a dark color to minimize the appearance of the tv.

Budget? no reflection on anyone or anything, but asking cause I don't know. Moving one aside might seem less a "big look/ but not built in." ?