To treat one average book you will need an airtight plastic container large enough so that it will leave at least two to three inches of space around the book on all sides. Make sure that the container has no handles or vents that could make it less than airtight. There are many inexpensive storage containers available for a few dollars that will meet these requirements. A wide selection should be available in the housewares department of any discount department store.
You will also need something to serve as a slightly raised (½"+) and perforated platform inside this box. This is limited only by your creativity, but something that works well and costs less than two dollars is a cooling rack. Yes, the same ones used for cooling fresh-out-of-the-oven cookies. These 9" x 12" racks usually come two to a pack. To make sure the rack will fit inside your container, I suggest that you buy these two items at the same time. They don't need to be a perfect fit; the rack just needs to lie flat on the bottom.
There are lots of workable alternatives to the cooling rack that can be custom fitted to your container, including a large tub if you want to treat several books at once. (An under-the-bed storage bin would work well in this situation.) For instance, most hardware stores carry a plastic grate, normally used for air conditioners, that is about ½" thick and can easily be cut with wire cutters, snips or heavy duty scissors. The platform I made for the purpose of this article was constructed out of a plastic gutter cover and some wooden shims. You could also use screening and square wooden dowels. Anything that will create a raised platform for your book and has ample ventilation holes in it will do the job, so hit the hardware store - or even your own garage - and improvise.
The last thing you will need is a box of baking soda. Plain old bicarbonate of soda, which will cost less than a dollar.
The procedure is simple:
Sprinkle the baking soda on the bottom of the plastic container to a depth of ¼". Put the raised platform on top of the soda and the book on top of the rack.
Seal the container and set it aside for a few days.
Just as an open container of baking soda will absorb odors in your refrigerator or freezer, it will also absorb them from your book. Depending on how bad the book smells, it could take longer - a week or two - but check the book periodically and give it a sniff test. Your nose will tell you when it is done. You will need to change out the baking soda every month or so. Just mark the date on the calendar or put a sticky note on the container itself.
Some people simply put the book into a Ziploc plastic bag, sprinkle in the baking soda, and seal it. This will work, but you'll have to clean all that powder off the book - an unnecessary step if you use the container and platform.
In place of baking soda, some people swear by other odor-absorbing materials such as crushed activated charcoal, kitty litter with zeolite, cedar chips, and laundry dryer sheets. They may even tell you to bury your book in these substances, but I wouldn't recommend it because you never know what chemicals or oils are present that harm your books. The advantages of baking soda fourfold: it's cheap; it absorbs odors rather than just masking them, has a neutral scent (so the book won't smell like flowers or freshly washed laundry); and it's very environmentally friendly - when it outlives its usefulness, you can pour it into the sink and it will help to eliminate odors on its way down the drain.