I don't know about the faded icons, but the plus and minus signs have to do with selecting your books via the tag browser: If you click on an entry the first time, it changes to a plus and the books in that entry get displayed. If you click on the entry a second time, it changes to a minus and the books
not in that entry get displayed. You can select multiple entries using the ctrl key. If you're unsure about what is getting displayed, take a look in the search bar- the tag browser constructs a search for your selection.
Edit: Damn, I got ninja'd
