First suggestion is to move the sofa. As it is positioned right now people sitting on the sofa will be focused on the pass-thru which seems really odd. Second piece of advice is unless you need the pass-thru wall it up. Having a pass-thru from a kitchen to dining room makes some sense. Have a pass-thru to the living room - not so much. If the pass-thru is walled up you should be able to rotate your sofa 90 degrees and place it against the wall so that the focus is into the living room.

Pass trhoughs are really dated and one into a LR makes no sense. I agree the placement of the sofa is odd . Do you have a drawing of what you are planning? The knotty pine dictates the wood choices and do you really have so many books they need a whole wall? If this shelving is being made to hold knick knacks then IMO forget it it will just look cluttered . Do you have TV in the LR ? We need a lot more info and some clue as to what this plan is .

Library walls don't usually have pass throughs. If you close it up, the library wall will look a lot more customized.

Finding matching knotty pine for new bookcases and getting it finished right will be difficult. Try taking a dark kitchen drawer to some office furniture stores and to the local Ikea if you have one. Look for a finish that is reasonably similar to your dark kitchen cabinets or one that looks good with the existing knotty pine ceiling.

If ready-made doesn't work for you, hire a custom cabinetmaker. They will deal with customization required by the trim, carpet (remove it under bookcases), and electrical outlets. Don't embed the light switches in the bookcases since it is awkward to stick your hand in a bookcase to turn the lights on and off.

is it because you need the light in the kitchen?

I would treat it just like a window.

Walling up the pass thru isn’t a bad suggestion, unless you love being able to look into the living room while utilizing the kitchen and perhaps need the light. I like Lyn’s pic with built ins around the opening. Without a floor plan I’m not sure how much space there is to work with, so I show it with a few feet of space between cabinets and back of sofa. Ignore the perspective of the cabinetry.

I think the question to be answered by homeowner is ‘what is purpose of passthrough’?

Guessing from the photos the kitchen does appear to be pretty dark and windowless. If it were my home, I’d probably want it open too, even though I’m not a huge fan of pass thrus. If budget allows OP could consider opening it all up, but sometimes that’s not an option and you have to work with what you’re given.

Thanks everyone who responded. Yes the kitchen is very dark and windowless without the pass through. The purpose is to let in light open the space up a bit. This sit he view from the kitchen. The pass through on the other side is bland and was trying to think of ways to make it a little more architecturally interesting. Just don’t know if we should go to route of built in surround or trim.
Vm

I saw this Pella window ad and it made me think of your pass thru. It may be an idea to consider to make it look like an interior window. It seems like the height of the pass thru would need to be heightened to make it look right. Might be an idea to play around with.

As an interior window:

Here’s a better idea

Here’s a view of what it might look like from the kitchen

You’d need custom, so the first step might be to have a carpenter take a look and provide options. Looks like the opening isn’t centred and creating symmetry will need to be taken into account. Imagine below with only your opening /you’d have to fill in below.

Easier option: We have an opening from kitchen to living room (done by last owners) and placed a console underneath and art on the walls. If you decide to do, frame the opening on both sides and suggest painting the same color as the wall - suggest lighter).

In-between options, wood stained to match your ceiling:

Couch placement might be a factor in its configuration…if you’d like advice, just provide a picture of the entire room.

The original poster wrote: "Yes the kitchen is very dark and windowless without the pass through. The purpose is to let in light open the space up a bit."

Would you consider a skylight or Solatube in the kitchen?

https://www.houzz.com/magazine/how-to-add-a-skylight-or-light-tube-stsetivw-vs~21634448

Shingle style home · More Info

I like Maureen’s idea of making it more of a room divider than a window.

The kitchen unfortunately is in the middle of the house with a second floor no option for a skylight

I like @Maureen 's Idea as it looks classy.

Is the living room an add-on from a previous renovation? I noticed a change in floor level and it looks like the ceiling is slanted. Was the pass-through once a window?
You seem to have lots of wafer lights and under counter lighting in your kitchen. It looks very well lit in your photo. I don't understand why you think it isn't well lit and needs natural light, but ok.
If you don't like the kitchen and want to change your living room and are stuck with the pass-through, is it time to look at your floor plan for your entire home and ask if it could be completely renovated?

In your renovation, will you be raising the floor level of the living room to match the kitchen? I am surprised this isn't important to you.

If you want it to look like a full-wall of a library, then filling in the wall is what is needed. If you don't want to do that, then my favorite solution is this one. But perhaps only partially, some of this on each side, left and right. Break up the big wide opening into thirds or so. Leave a complete but narrower opening between two areas filled in like this. Put decorative wood paneling on the wall below and above. The look will create a little vignette for a globe on a floor stand or an antique book stand for a large book. The area above on the wall would want a downlight.