The design is really space-saving.
Structurally the bookcase is a bit wobbly when assembled, so not as sturdy as expected, but as it interlocks together, it will be quite safe once in use.
The only other comment is about a minute of panic once the first package assembled and realised the second package is identical - all well once figured out that for the interlocking corner bookcase you assemble the same unit but put it upside down... Phew, all well in the end.