@
Henning - for the first two (series: rating and series: description) you could add two custom columns:-
series_rating/Series Rating and
series_description/Series Description, then add empty zeroeth books (i.e. Blah Series [0]) and put the series rating and description in that book, you could hide those columns in the Book List and only show them in Book Details.
For the other two, virtual libraries are based on search expressions which could be something like
series:"=My Series", but you could end up with lots of VLs. A simpler solution might be to use the Similar books tool:- e.g. Alt+S will show all books in the same series as the selected book.
And, have a look at the View Manager optional plugin, see ==>>
Index of plugins.
BR