So I found a roombox kit that looked interesting, advertized as a library, it's really called "Sam's Study."
It arrived Friday, and I've managed to paint most of the base and two walls. The paint they provided was eggshell, but I didn't like the holidays or the places where I could see the original board underneath after two layers, so it got a spray coat of white enamel. I'm tempted to find another color, something warmer, to paint the wall panels with.
I've also started assembly of the first cabinet. The blue cabinet has a clear plastic sheet inserted as a window.
This is the first cabinet assembled. As you can see, this looks nice together. However, there's a gap between the two angled bookshelves. I'm likely to fill the gap with a thin square dowel.
I had a mishap during construction, as it wasn't clear on how this all fits together, there are little tabs in the bottom piece that go to the back, and I put together the big left bookcase backward. So I disassembled the unit before the silicon glue set, and put it together right. However, I didn't have anything to mop up the silicon glue, so I had to run out for cotton swabs and rubbing alcohol to clean up the dried glue.
Sadly, the rubbing alcohol also removes some of the pigment from the boards. I will probably have to touch this up before I put the books in.
The applicator tip for the glue is not very good, I'm going to have to find something finer or just use flat toothpicks dipped in the bottle. And a squaring jig. Definitely a squaring jig.