該是下面幾種情形:
1. The knowledge is new for even experts. Then it is worthy for the interested reader though the knowledge is revealed in "difficult "(thus technical or semi-technical) language.
2. Knowledge old, but the writer offers with new insights. Again, in a "difficult" language. Still worthy for the motivated readers.
3. Old and without new insights but servers the literature as important constituents. In this case the knowledge should be restated in "easy" ( thus non-technical language ) otherwise they will fail to function.
Naturally, 劉慈欣 is with 3.
Regarding 立 's work, since readers here (suposely well educated but not experts) declare that they could not follow the knowledge in it, therefore it isn't with 3.
Then, which is it? 1 or 2 ?