For the obvious reason that the upstairs landing is blocked in by the bathroom and living room walls, I found it easier to install the interior of the smaller bedroom and the landing interior at the same time, glue the staircase in place, then add the bathroom and living room walls.
Here is the smaller bedroom. It's not 100 percent complete - I still need to install stair railings and fix the gap under the cove molding on the left side - but I love how it's turning out.
Here is a glimpse of the landing from the front of the house. (I couldn't get a good angle on the bathroom wall, stairs, etc.) I initially painted the window frame white, but it looked much too plain. Glossy black paint to the rescue!