The tags are probably not muktze machmat chesron kis. In order for something to attain that status of muktze, it usually must be quite valuable (ex. a brit milah knife, etc.) so that the only conceivable thing you could do with the object is either prohibited or just not use it at all. (Shulchan Aruch Siman 308.1)
It appears to me however that it does fit quite well with the definition of a kli shemelachto lissur. Of course, then you could move the tag if you needed the space it occupies or needed it for a permitted task.
There is a question whether the book becomes a basis due to the tag-and one standard answer would be no because the tag serves the book not vice versa, as such, whenever we move the book, moving the tag should be okay because it is tiltul min hatzad ldavar hamuter. (See Aruch HaShulchan Siman 309, 5 and 311 21). The distinction here, is that a book would presumably be a kli shemelachto lheter and now you can move the book to protect it.
But are books muktze?
If we are talking about "books of wisdom" (ex. science, philosophy), the Shulchan Aruch brings down a debate (Siman 307 ,17 and 308 50) if we can study from them or move them on Shabbat. See the Mishna Berura that says in Siman 307 there that we are accustomed to be lenient, (hence it would be a kli shemelachto lheter) but says that for a yira shamayim (a God fearing individual) it is appropriate to be stringent.