Furnishing depends on what you plan to use the room for....

no sense suggesting bookcases if you do not want books in there!

I have a long,well not as long as yours, and narrow, but a bit wider than yours, living room. I am, I think, 14feet wide so I do not know if this would work for you, but we floated all the seating away from walls because one wall has two windows and a fireplace and all the other walls have double doorways. We went with a non deep sofa, two chairs and an ottoman instead of a sectional to help the walk flow threw this room since it is between three well used areas. Also sectionals are good for family but a bit awkward when entertaining and this is not only my tv room but also our main living room for company too.

Do you have any photos?

Here is a diagram which will give you a idea of a floating room. Essentially it means you move the furniture into the room and away from the walls. In this version the sofa was placed running the same was as the length of the room. If I had your room I would face two sofas away from the longest wall and facing each other so that they come off the wall into the room like two items across this box I'm typing in. Put them not the length but the width. The width is the vertical part of this box. Then add a large coffee table with lamps. In one corner I'd add a nice reading chair with a standing lamp and at the other end maybe a desk or game table. Google floating living room and then go to images which is on the google page and youll see dozens of rooms for inspiration. Good luck.

Here is a link that might be useful:

Divide it up into smaller "rooms" with some furniture places perpendicular to the walls.

A floor plan would help, because a lot depends on how it connects to the rest of the house.