I am really leaning in favor of prefinishing the pieces of my bookshelves - at least the stain and a coat or two of finish. My (3/4" nominal) shelves will fit into 1/4" deep dadoes. The shelves will fit into the dadoes at their full thickness. Counting the tops and bottoms as "shelves", there are 20 pieces.
I thought it would be a really great idea to make "end caps" - 2x2 material as long as the shelves are deep, with dadoes cut in them - to both "mask" the shelf edges and allow me to stack the prefinished shelves in a small space. And it would be a great idea, but I'd need 40 of them, or a significant fraction of 40 at least, and that seems like a lot of wood and a lot of work.
So now I'm wondering about painter's tape. Is there any reason I couldn't tape the ends of the shelves - deliberately overshooting the area that will go into the dado by a little bit - then cut away the excess with a straightedge and an X-acto knife? I imagine locating the line so as to have it end up just inside the dado after assembly.
As for the uprights, was thinking I could avoid getting stain and finish in the dadoes by putting strips of ply in the grooves while I coat them. In fact, that might also facilitate stacking, especially as only two of the eight uprights will be finished on both sides.
Any better ideas?
By the way, many thanks to whoever it was that suggested a pattern bit for the dadoes. I took me a while to make the jig, but once I got going it was like clockwork.