If you've read the Strange Items Found in Books, you can imagine what this section will be like.
Sometimes when books are returned, they come in those plastic WalMart bags. One day my supervisor untied a bag of returned books and discovered they smelled bad. As she took the books out, the smell got worse. The cause was soon found. The bottom book in the bag had vomit on it. I kid you not. The people who had returned them were still in the library, so we asked them about it. The Dad, who didn't bag up the books, was
furious. We never did find out who it was that puked on the book, though.
One gentleman, who you'll find in my Weird Patrons section, brings back books that smell like cats have "marked their territory" on them. There is nothing quite like opening a plastic shopping bag with books that smell like cat pee--fortunately.
Another nice man always brings in books that smell like they've been stored in a smokehouse for two months--well, one filled with cigarette smoke, anyway. I'm allergic to cigarette smoke, so this is particularly annoying.
Recently, a woman turned in two cooking books that were soaked with grease. They smelled like some kind of cooking oil that I can't think of the name of at the moment. The books were really gross. The pages were almost transparent.
We also get some books turned in with unidentifiable smells that are just not describable.