I finally located a used copy of Dame Kathleen Kenyon's Digging Up Jericho, a vital component to some biblical/archaeological research I've been doing. The bookseller sent me a faintly mildewed, yellowing copy that was a library discard, for which I paid a semi-reasonable $14.50 (happily; I've been trying to get this book for months.)
Old books that have not been cared for stink, and over the years this is what I've discovered while trying to detox them:
Never use liquids or anything strongly scented like perfume to detox a book. Febreze is for fabric, not pages. Perfume has alcohol and other agents in it that can stain and cause more harm to the book.
People advocate sealing the book in a large bag or box with several crumpled sheets of newspaper or inserting folded sheets of newspaper every couple of pages or so, changing the newspaper frequently. This is slow and I've never found it to work completely for me.
Sun can bleach out a lot of odors, but it can also harm delicate old books. Not recommended.
Putting the book in a bag of cat litter can actually create more problems, depending on the brand. Some litters are treated with chemicals that can leave spots and stains of their own. Also not something I'd try.
Talcum powder: I can't find any unscented, or I'd give it a whirl.
My method: I make sure the book is completely dry*, then I use a soft-bristle brush on any visible mildew flakes and brush out what I can. I spread a small amount of cornstarch on each page, the end pages, the cover and down the spine, wrap the book in tissue paper and let it sit undisturbed for two or three days. I then shake out and then brush out the cornstarch. It completely absorbs the odors and leaves no residue.
I don't recommend anyone try to detox a truly valuable book; hire a professional conservator to restore it instead. Minnesota Historical Society has some info on that here, and Antiques Roadshow has a good article on the subject here.
*How to dry a wet book, via University of Delaware Library.