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!)
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!)