A bookmark, the inseparable friend of a book
It is increasingly common to include a bookmark in a book edition.
Many publishers, when editing a new work, decide to also print a bookmark included in that book, so that both constitute a single pack and the bookmark can not be sold separately. In this case, the bookmark serves a very relevant marketing function. The contents of this bookmark are closely related to the book: they either highlight some outstanding feature of the book, summarize some aspects of the work, or simply encourage the reading of the book by using attractive advertising messages...
The fact that the book we have just bought in our usual bookstore includes a bookmark is something to be grateful for. It's annoying to start a new book and, when it's time to stop reading, not to have anything at hand to bookmark the page we've just left.
However, in many cases, the books we purchase do not include bookmarks. In order to remedy this situation many booksellers include their own bookmarks, as a courtesy to us as customers. Such branded bookmarks serve as promotional tools for the bookshop, in which booksellers include their contact details, the bookshop's name and available sections, etc.