(These have to be emitted separately so that the depth will be consistent and the corners right angles rather than rounded as will happen if they are unioned)
One issue when importing elements formed from really large circles is that even with a very large number of segments used for describing the circle one will have a faceted appearance:
Now I just have to make … (well, I don’t really want to tally that up just yet — remember, the correct translation of “too many books” is "not enough bookshelves) — instead I’m going to work up a file for a half-size variant, so that one could make a rectangular stack as if with bricks.
It fits nicely into a paperbox, leaving room for a second, with room for padding (or other books) on top of or beneath it, so the moving aspect should work well.
Here are 3 files for cutting it (slightly modified from when I cut, but should still work) from Lauan plywood sheets used for underlayment and readily available in inexpensive 2x4 sheets at any lumber yard. Splinters when cutting, hence the modification, but workable and inexpensive enough.