I feel like I either want more windows, or fewer. You've got a repetition of the window element in here, but with only two (really) it feels redundant, not like a graphical statement. If you had 3 or 4, it would feel like a "repeated motif" or something, with the windows building on one another visually. With a single one, we can concentrate on the architectural details, the textures, and so on of the window. With just two, it's neither one nor the other.
I think the slant is an optical illusion, possibly combined with a little lens distortion. The vertical in the lower center of the frame looks pretty straight to me, but the whole frame definitely "feels" like it's leaning to left. Not sure what to do to fix that.