Floorstanding or bookshlf speakers?

Your room is big enough for Floor standers. I have seen B&W Signature 800's mentioned in rooms half your size!?!?! IMO your room would be fine, since you still need stands for book shelf models anyhow!

Definitely big enough for floor standing speakers. I think you would need to fire them along the length of the room, as the short dimension would leave you too close though.

The only possible problem would be if you got full range speakers (down to 20hz) and then listened to them very loud. (The room might enhance the bass to make it a bit booming. However, since you have bookshelves on three of the sides, with books on them presumably, I think this would mitigate even that to some degree.)

I say go for the full range, as they are more satisfying than the bookshelf type, (in my opinion,of course!)

I'd guess that bookshelves filled with books arround the room can only be a plus for a listening room. They kill wall reflections.
I guess you'd need a good and heavy speaker such as PSB stratus Goldi that would stay firm on the floor in case you want to rich for book bihind the speaker:-).

I like the idea a hi-fi system with floorstanding speakers IN A LIBRARY!

Seriously though, I think the room is big enough for floorstanders. You may want to consider a large area rug on the floor to help with sound and comfort. Definitely have the speakers facing the long dimension of the room. This will give you a lot more options for speaker placement. With such a long room, you may be able to achive good sound with the speakers 3 to 4 feet (or more???) from the back wall. That way you will be able to walk behind and to the sides of them to get at the books if this is necessary. Some floorstanders have a small footprint and others do not. If you think space will be a problem, go with the floorstanders that have a smaller length and width.