- Don't treat it as one room: divide, perhaps using a corner arrangement but treat it as one continuous space ...
- Think of traffic flow and keep traffic to one side
- Try and avoid sitting looking straight at nearside wall, looking the length of the room will be more satisfying
- Have a piece of furniture near the end of stop the eye
- Where is the focal point? It's best not on the end wall
- Decorate the long walls with cool light colours
- lighting - recessed shelving, towards groups of items.
- small stools, cubes.
- Put the bookshelves on short walls
- However, if you do have to have bookshelves on the long walls, start half way up, so floor space seems wider as not all the room is narrowed
See also: http://tlc.howstuffworks.com/home/how-to-work-a-long-skinny-room1.htm