I've never seen contact paper on a library book. Not in the Uof Alaska system, nor the Anchorage Public nor School District libraries, not the Linn-Benton (Oregon) public libraries, nor the Alsea School District J (Oregon). I've not gone into the OSU nor LBCC libraries here in Corvallis.
What I've seen are clear cellophane folded around the dust jacket of hardcovers, and often then that taped onto the hardcover. And that's been the case on books from a number of libraries I've not been too but have checked out materials from via Inter-Library Loan - over a dozen in my undergrad, including Lake Geneva Public Library. (One of which was checked out in 1973 by an EG Gygax, according to the pocket in back.)
Also, all the contact paper I've used? The glue does NOT come off easily, and takes ink with it.