Hardcover books are much easier to clean than leather-bound, cloth-bound or paperback books because the hard cover can withstand being rubbed down with alcohol. The most common "dirty book" problems are related to mildew that grows within the pages, due to the book being stored in a damp environment. With a few mildew-removing tips and tricks, combined with a simple cleaning of the cover itself, you can have your hardcover books clean in no time.
Deodorise the hardcover book by first searching for any mildew spots on the pages and then covering them with cornstarch. Let the book sit for 24 hours. Shake out as much of the cornstarch as you can.
Use a magnetic dusting cloth, such as a Swiffer, to pick up the leftover cornstarch as well as any excess dust or dirt from the pages. Remove any marks or stains from the pages with a white vinyl eraser.
Pour rubbing alcohol into a cotton ball and squeeze out until it is no longer dripping. Never pour the alcohol directly onto the hard cover of the book. Gently wipe the hard cover of the book down with the cotton ball, using small circular motions. Use a dry cotton ball to buff away any excess moisture the rubbing alcohol leaves behind.
After you have cleaned your hardcover books, make sure to store them somewhere with little to no humidity to ensure that they don't become musty or grow mildew again. Dust the outside of the books weekly to avoid build up, and take extra care when handling the books---excessively oily fingers or hands can dirty a book quickly.