Thanks a lot for all the information and the pictures.
At the moment I am making a similar construction. It is not a bookcase but the frame is very much the same. And your post made me pause a bit and think it over again. Now, with your photos, I’m not confused but confident.)) So, tomorrow it will be time for chopping mortises.
Thanks for the photo.
Rather thin panels. Did you thickness (I suppose this is not a correct word) them with a hand plane or pass them through a planer?
Excuse my asking so many questions; what thickness the boards were when you glued them?