This is not a best picture, do you have the one with the window part?

A window view would make it easier to help, but I'd say bookcases that aren't as deep as the firplace that aren't as wide as the space between the fireplace and the window. Just a simple maybe 24" wide and 12"-16" deep on both side of the fireplace would work.

I think this picture has a better view of the window

I agree with interior_decorating_diva. Maybe a built-in that's more like a piece of freestanding furniture with some space between it and the window wall and the fireplace. I'm not so sure about both sides of the fireplace as it appears the walls are different dimensions. And keeping it detached at the sides will allow you to play with the height as it appears the window head, fireplace trim and walkway all don't align.

i compliantly agree with comment above, plus i sagest that one on the left can be with open side so you can put some decor items there

Will you have a t.v. in the room? If so maybe have bespoke units made in the same style with aged off white paint finish. One could
be an open bookshelf and the other a unit with doors to house the t.v. and accessories. Much nicer than the t.v. on the fireplace.

I don't know that you need to build in a bookcase or shelves. You could find a nice bookcase that is freestanding furniture, perhaps with glass doors, and place it in the space to the right of the fireplace below the light.

There are a couple of features that don't really go with your style: the column, if it is necessary for support, should be replaced with a square one, and the lights that flank the fireplace should be changed IMO.

Builders are right. If you put next to the fireplace is traditionally symmetrical bookcases, it's the right cabinet will close part of the space near the window. The solution may be to set high but narrow bookshelves.

hey ym2000, why not do a 'ladder' type of shelving either side that is open. that would incorporate your shabby chic vibe. i think they could be diy-ed. you could place the 'ladders' close to the fireplace and have some space between them and the window. if you decorate them sparingly it will help with the classic look of the fireplace area. good luck!

- In this situation, we usually graduate the depth of the shelves as you get closer to the window, perhaps starting with a 24" d. base cabinet next to the fireplace with 12" d. shelves over the top, and then a 12" d. bookcase held a foot off of the window at the right.

There are companies that specialize in "shabby chic" cabinetry for retail applications, but I don't see why they wouldn't work in your home. A left and right hand version of the cabinet below could work . . .

here's their website: http://www.vintagegardens.net/store_fixtures1.htm

Or have you thought about floating wall shelves? At least on the right, that would be a great way add storage without blocking the window.
It also leaves you a lot of freedom to customize the shelf color/hardware to match your space and style exactly.

Thank you so very much for your replies!
We did buy the house and slowly unpacking - seems like that process will take months! For now, we used all the little pieces we had to fill the space on each side of the fireplace... I do like the idea of not doing matching bookcases but something either floating bookshelves or a standalone rack on the right side.
We are changing the big picture above the fireplace - it feels like it needs something bigger and maybe in color

It looks so much better than before! Great progress!

Have you thought about trimming the wall to match the trim on the fireplace?