Yes....a slanted room. My house and both houses on either side all have matching sunrooms built on top of the original decks, all sloping away from the house. Clearly they were designed that way but for what purpose we'll never know. My neighbours use theirs as a mudroom and laundry room, mine is painted and decorated as a sitting room.
Currently I have a couple of couches and an easy chair, coffee and end tables in there but I still find it quite bare. I'd like to add some additional furniture, bookcases for my collection of garden books and some cabinets for storage. So far it's been a challenge to find anything that works along the side walls because of the slope.
I was considering custom making a few pieces that would account for the slope and hopefully fit just right, either that or buying a few pieces and either some adjustable legs or cutting the legs to accomodate the un-even-ness of the room. My concern in doing that is that it will end up accentuating the slope and making it more visually noticable in comparison with the straight lines of the furniture.