I have read the 2 links provided - granted, quickly. Respectfully, that may not do it. If it does, it seems it doesn't overcome the problems cited:
1. Any use of tags presently means that the tag has to compete with all the other tags (thousands). Regardless, from what I can see, any tag is buried among all the other tags i.e. doesn't stand alone on the left side, as is the case with, say, "Authors" i.e. maybe I'd like a collection on the left side that organizes books for "Children's".
2. Maybe I missed it, but I don't see a way without the use of tags to easily eliminate the objectionable titles within the choice of any author. For example, let's say that I've identified all books withing 10 authors, except 1 of the authors has 25 titles when I'm only interested in 1 of this author's book.
Am I missing something pls and thks?