I was going to say the same thing as SG.  Even though the cabin may be leaning, you can see horizon on the left which angles down.  Depending on what program you use, you can usually custom rotate, in this case clockwise a couple degrees until the horizon looks level.  Then it will be obvious that only the cabin is leaning.

Btw - I really like the subject and color too - looks a little different than sepia to me, more of an antique gray/sage green.  Whatever it is, looks good with this old cabin.