have you considered free standing units rather than built in?

closed storage rather than shelves you have to merchandise?

Note that the dimensions on either side of the window are 37” x 95”.

Yes freestanding is fine. Hoping for a more modern or midcentury look in keeping with the house.

We also have a lot of books…

Looks like there is baseboard heat that will affect the placement of the bookcases. Make sure to take that into consideration

Thank you. Yes, although the house has a heat pump so the baseboards are only back up.

Very nice!

It's hard to know what you expect to keep in the space. Are you hoping to keep the black carved cabinet, desk, chairs, whatever that is under the window and tulip table in this space? If not, I'd recommend long bookcases about 3.5 -4 feet tall in a wood that matches your chairs. You can put decor on top and have books and other items on the shelves.

I’d add a bookcase or shelving on this wall.

On the other end add a seating area to read (and enjoy the view).

I've used modular bookcases with metal legs to accommodate baseboard heating before. They can be configured to suit your needs.

Something like this.

@Expobaby Love these. Do you know what brand these are? Lovely design. Also wondering if you'd recommend on either side of the window or on one of the walls?

@Maureen Thank you! Do you know what brand or on what site these bookshelves are available--very lovely.

I found that picture on Westelm, but many companies carry similar modular bookcases. I'm usually a fan of flanking windows, but I'm leaning towards placing the bookcase on the wall. The nice thing about modular is that it's easy to move around to see what you thinks works best for you.

I believe they are custom and if handy/or could hire, you’ll save a lot of money and you’ll end up with the dimensions and stain you prefer. https://nikkianneluxuryliving.com/diy-built-in-bookshelves-weekend-project-guide/

Might be a good idea to compare custom vs store bought‘s advantages and costs.

How many linear feet of books do you want to put in here? If you have photos of the books in their previous house's bookcases, you can estimate from the photos.

I agree freestanding on either side of the window is best but I like books usally in a space where you aslo read them , with your space probably by the rear windows . Are you planning to fill with only books ? I did one clinets home with low bookshelves all along one wall with great art above them . Visually just a nicer look for her and not so inyour face tower of books that are always a bit of eye clutter for me.. I love my books but not as decor This is kind of what I did for that client you could maybe even do it in front of the window